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Authorized for public release by the FOMC Secretariat on May 6, 2015

Interest on Reserves: An Analytical Framework1


April 2008




1

Huberto Ennis (FRB Richmond) and Todd Keister (FRB New York) authored this paper as part of the
work undertaken by the Interest on Reserves (IOR) workgroup.

Authorized for public release by the FOMC Secretariat on May 6, 2015

This paper presents a simple, stylized framework for understanding the monetary policy
implementation process. An explicit mathematical model of the demand for reserves by
commercial banks is developed and presented using graphical methods. The objectives
of this analysis are to illustrate the basic economics behind each of the proposed policy
regimes and to highlight the similarities and differences each has with the current U.S.
regime. The framework is also useful for analyzing the extent to which the different
proposals are consistent with overall policy objectives.
We begin by presenting the basic framework in the context of the current U.S. policy
regime. In the first section we describe the framework in its simplest form, which
abstracts from reserve maintenance periods, daylight credit, and other important issues.
In the second section we show how the framework can be extended to address these and
other issues. In Section 3 we show how each of the policy proposals under consideration
can be illustrated and analyzed in the context of the framework.

1.

THE BASIC FRAMEWORK

The central component of the framework is a simple model of the demand for overnight
reserves. In this section we describe the model in detail and discuss some of the issues
abstracted from in the analysis. We then present a graphical illustration of the current
U.S. policy regime; this case will serve as a base line for the analysis in the following two
sections.
1.1 A SIMPLE MODEL OF RESERVE DEMAND
The model presented here focuses on nonborrowed reserve balances, that is, funds held
by commercial banks on deposit at the Federal Reserve that have not been borrowed from
the Federal Reserve. Banks hold these reserves primarily to satisfy reserve requirements
although, as discussed below, other factors such as the desire to make interbank payments
also play a role. Banks face uncertainty about the flows into and out of their reserve
accounts and, therefore, are typically not able to exactly satisfy their reserve requirement.
Instead, they must balance the possibility of holding excess reserve balances – and the
associated opportunity cost – against the possibility of being penalized for a reserve
deficiency. A bank’s demand for reserves results from optimally balancing these two
concerns. Banks are assumed to be risk neutral and to maximize expected profits.
The basic elements of the model are as follows:
Interbank Market. Each day, commercial banks can borrow and lend reserves in an
interbank market. The Central Bank conducts open market operations and can thereby
change the total supply of reserves. We model this market as being perfectly
competitive, which is a reasonable assumption for most of the day. Toward the end of
the day, this market closes and banks are unable to make further trades.



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Payment Shocks. After the interbank market has closed, each bank experiences a payment
shock P that affects its end-of-day reserve balance. The value of P can be either positive,
indicating a net outflow of funds, or negative, indicating a net inflow. The assumption
that the interbank market closes before the payments shocks are resolved is a simplified
way of capturing the imperfections in the interbank market that become more severe near
the end of the day. The important feature of the model is simply that banks are unable to
perfectly target their end-of-day reserve balance. Uncertainty about the end-of-day
balance creates a “smooth” demand for reserves.
We assume that the payment shock P is uniformly distributed on the interval [P, P] . The
lower bound of this interval, P, will typically be a negative number, meaning that lateday payment inflows are possible. We study the effects of other distributional
assumptions later in this section. The value of this shock is not yet known when the
interbank market is open; hence, a bank’s demand for reserves in this market is affected
by the distribution of the shock and not the realization.

Reserve Requirements. To keep the presentation simple, we start with a model where
reserve requirements must be met at the end of each day. Let K denote the level of
reserves a typical bank is required to hold. We discuss multi-day maintenance periods in
Section 2.2 below. One can also think of the case we study in this section as applying to
the last day of a multi-day maintenance period. In this case, the reserve requirement K
should be interpreted as the quantity of reserves the bank needs to hold on the last day of
the maintenance period in order to satisfy the overall requirement, given the reserve
holdings on previous days in the period.
If a bank finds itself holding fewer than K reserves at the end of the day, after the
payment shock P, we assume the bank must borrow reserves to cover this deficiency at
some “penalty” rate rp. In the current U.S. system, rp can be thought of as the rate
charged on discount window loans, adjusted to take into account any stigma effects of
borrowing from the discount window. Alternatively, a bank may instead pay the reservedeficiency penalty, either by choice or because it does not have sufficient collateral
posted at the discount window. For our framework, the important feature is simply that
the bank is forced to make up any reserve deficiency at a penalty rate of interest. This
rate could come from the discount window, a deficiency charge, or even from borrowing
at a high rate in the Fed Funds market at the end of the day. Whatever the source of this
penalty may be, we use rp to denote the rate a bank must pay to cover the deficiency and
satisfy its requirement K.
Daylight credit. In this section we assume that daylight credit is freely available to banks
at no cost, so that the cost to the bank of making payments during the day is independent
of its overnight reserve position. We study the case where daylight credit is costly and
show how this changes the analysis in Section 2.3 below.
Discussion. The simple model used here abstracts from many features of reality. For
example, we do not include vault cash in the analysis and, therefore, the required reserves
in this framework should be interpreted as the requirement net of vault cash holdings. To

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the extent that vault cash holdings are independent of the overnight rate, at least over
short time horizons, including them in the model would have no effect. We also abstract
from contractual clearing balances that, once set, act much like required reserves.
Other assumptions are perhaps less innocuous. The framework implicitly assumes, for
example, that the only cost a bank faces when holding reserves is the opportunity cost of
not lending the funds out. In reality, holding a much larger quantity of reserves might
require a bank to raise more deposits and subject it to higher capital requirements. For
most of the options under consideration, however, such effects would likely be small.
Literature. The model here uses the basic approach to reserve management introduced in
Poole (1968). More recent contributions to this literature include Furfine (2000), Clouse
and Dow (2002), Bartolini, Bertola and Prati (2002), and Whitesell (2006a). The model
closely follows that in Ennis and Weinberg (2007).
1.2 THE CURRENT POLICY REGIME
In the current U.S. policy regime, the FOMC selects a target for the overnight interest
rate and instructs the Open Market Desk to adjust the quantity of reserve balances in
order to achieve that target. Banks can borrow reserves from the discount window at a
rate that is 100 basis points above the target Federal Funds rate. The penalty rate in our
analysis rP should thus be thought of as being at least 100 basis points above the target
rate. Banks earn no interest on their reserve holdings.
This subsection presents a graphical illustration of the model demand for reserves under
such a policy regime. Figure 1 depicts an individual bank’s demand for nonborrowed
reserves. To draw this curve, we ask: Given a particular value for the interest rate, what
quantity of nonborrowed reserves would the bank demand to hold if that rate prevailed in
the market? In most circumstances, a bank would be unwilling to hold any nonborrowed
balances if the overnight rate were higher than the penalty rate rP. If the market rate were
higher than rP, banks would choose to meet their requirements entirely through
borrowing from the discount window. In fact, they would like to borrow even more than
their requirement and lend at the higher market rate, but this fact is not important for the
analysis. The important point is that there should be essentially no demand for
nonborrowed reserves for any interest rate larger than rP.
For interest rates below rP, however, banks will choose to hold some nonborrowed
reserves. This demand is “precautionary” in the sense that banks choose their reserve
holdings to balance the possibility of falling short of the requirement against the
possibility of having extra reserves that earn no interest. A bank will always choose to
hold at least K+P reserves in this case, because P represents the smallest possible lateday outflow of funds from the bank’s reserve account. (Note that the diagram is drawn
under the assumption that P is negative, so that -P is the largest possible late-day inflow
of funds.) If the bank held fewer than K+P reserves, it would be certain to need to
borrow at the penalty rate overnight, which would not be an optimal choice when the
market rate is lower than rP.



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If the overnight rate were very low – close to zero – the opportunity cost of holding
reserves would be very small. In this case, each bank would hold enough precautionary
reserves so that it is virtually certain that unforeseen movements on its balance sheet will
not decrease its reserves below the required level. In other words, the bank will hold
K + P reserves in this case. If the overnight interest rate were exactly zero there would
be no opportunity cost of holding reserves. The demand curve is, therefore, flat along the
horizontal axis after K + P .

Figure 1: Basic Analysis of the Current Regime
Overnight rate

rp

target
rate
demand for reserves
required
reserves

0

K+P K

target supply

K+P

Nonborrowed
Reserves

In between these two extremes, the demand for reserve balances will vary inversely with
the market interest rate; this portion of the demand curve is represented by the
downward-sloping line segment in Figure 1. The curve is downward-sloping for two
reasons. First, the market interest rate represents the opportunity cost of holding reserves
overnight. When this rate is lower, finding itself with excess balances is less costly for
the bank and, hence, the bank is more willing to hold precautionary balances. Second,
when the market rate is lower, the relative cost of having to pay the penalty rate on a
reserve deficiency is larger, which also tends to increase the bank’s precautionary
demand for reserves. 2
We assume for the moment that all banks are identical, so that the aggregate demand for
reserves looks exactly like each individual bank’s demand. Figure 1 thus also represents
2

The linearity of the downward-sloping part of the demand curve results from the assumption that the
payment shock is uniformly distributed. We study the effects of other distributional assumptions below.



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the total demand for non-borrowed reserves in the banking system, measured in per-bank
terms. We discuss some of the issues that arise when banks are heterogeneous in Section
2.4 below. The equilibrium interest rate in the interbank market is determined by the
height of this aggregate demand curve at the level of reserve balances supplied by the
Central Bank. As shown in the diagram, there is a unique level of reserve supply that
will lead the market to clear at a given target rate; this level of reserves is labeled the
target supply.
Note that there are really two policies available to affect the (equilibrium) market rate:
changing the supply of reserves and changing the discount rate. Suppose, for example,
that the Central Bank wishes to decrease the market interest rate. It could either increase
the supply of reserves (say, through open market operations), leading to a movement
down the demand curve, or it could decrease the discount rate, which would tend to rotate
the demand curve downward while leaving the supply of reserves unchanged. Both
policies would – all else being equal – cause the market interest rate to fall.
In the current policy regime, the Federal Reserve sets the discount rate a fixed distance
(100 basis points) above the target rate during normal times. In this case, changing the
target rate involves an automatic change in the discount rate and, thus, an automatic shift
in the demand curve. As a result, whether or not increasing the market interest rate
requires a significant change in the supply of reserves depends on the elasticity of
demand and other details. In general, no major change in the supply of reserves is to be
expected. This fact helps explain some of the difficulties involved in empirically testing
for the “liquidity effect” of open market operations (see Carpenter and Demiralp, 2006,
and the references therein).
During periods of turmoil in financial markets, the stigma associated with borrowing
from the discount window may increase. 3 In terms of Figure 1, an increase in stigma
would be captured by an increase the penalty rate rP and, thus, would cause the demand
curve to rotate upward. Such an increase in demand would tend to increase the overnight
interest rate, leading the Desk to increase the supply of reserves in order to bring the rate
back down to the target level. In this way, the figure shows how periods of turmoil or
increased uncertainty in the financial system will tend to be associated with higher levels
of reserve holdings, as well as with a steeper demand curve for reserves.
1.3 UNCERTAINTY AND THE SHAPE OF THE DEMAND CURVE
The fact that the downward-sloping part of the demand curve in Figure 1 is a straight line
derives from the assumption that the late-day payment shock is uniformly distributed.
While this assumption is perhaps not the most realistic, it is useful for understanding the
overall shape of the demand curve, as demonstrated above. To draw the curve in Figure
1, we only had to determine two points: where the curve diverges from the rate rp and
3

Suppose, for example, that market participants believe recent movements in asset prices may make one or
more banks insolvent, but do not know which banks were holding the relevant assets. A bank may then
worry that if it borrows at the discount window, knowledge of the borrowing will leak out to market
participants and lead them to infer that the bank is in poor financial condition.



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where it hits the horizontal axis. The demand curve is then constructed by connecting
these points with a straight line.
Under different distributional assumptions, the demand curve may have more
“curvature”, but the overall shape will remain exactly as in the figure above. In
particular, for any distribution of the payment shock with support [ P, P ] , the demand
curve will be flat at rp until the point K+P and will be flat on the horizontal axis after the
point K + P . Between these two points, the demand curve will always be downward
sloping. Different distributions merely change the shape of this downward-sloping part
of the curve.
Suppose, for example, that the distribution of the late-day payment shock is humpshaped, like the orange curve in the left panel of Figure 2. In this case, moderate values
of P are more likely to occur than extreme values near either P or P . How would the
demand curve change if the bank faced this type of uncertainty instead of the uniform
distribution studied above?

Figure 2: Curvature of the Demand Function
probability

overnight rate

rp

non-uniform

non-uniform
uniform
uniform

P

0

P

P
0

K+P

K

R

K+P

The right panel in the figure presents the corresponding change in reserve demand. To
understand the shape of this new demand curve, consider first a level of the overnight rate
slightly below the penalty rate rp. What quantity of reserves should the bank hold if this
rate prevailed in the market? We argued above that the bank should hold at least K+P,
since if it held less than this amount it would be certain to face a deficiency after the
payment shock is realized and be forced to borrow at the penalty rate. In addition, the
bank will hold a small amount of “precautionary” reserves above the level K+P. In doing


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Authorized for public release by the FOMC Secretariat on May 6, 2015

so, the bank exposes itself to the possibility of being left with excess reserves at the end
of the day, which would occur if the realization of P is near P. However, holding more
reserves also decreases the amount the bank would have to borrow at the penalty rate for
other values of the payment shock. A reserve balance slightly larger than K+P optimally
balances these two concerns.
Under the orange (non-uniform) distribution depicted in Figure 2, the probability of a
payment shock near P is very small. Compared to the uniform case, therefore, the bank
is less concerned about a large payment inflow that would leave it holding excess
reserves at the end of the day. As a result, the bank is willing to hold a larger quantity of
reserves, which is why the orange demand curve in the right-hand panel lies above the
blue line for values of the overnight rate near rp.
Now suppose the market interest rate were close to zero. In this case, the bank will
choose to hold almost K + P reserves in order to prevent against the possibility of a large
payment outflow that will force it to borrow at the penalty rate. How much less than
K + P the bank chooses to hold will depend on the likelihood it will be forced to borrow
after the payment shock is realized. Under the non-uniform distribution in the figure, the
probability of a large payment outflow (close to P ) is very small. As a result, the bank
will hold fewer reserves than it would in the uniform case, where large payment shocks
are more likely. This corresponds to the fact that the orange demand curve in the righthand panel lies below the blue line for values of the interest rate near zero. 4
For the issues studied in this report, the specific assumptions about the distribution of
the payment shock are largely unimportant. In what follows we use the assumption of a
uniformly-distributed payment shock solely because it makes the graphs cleaner and
easier to read. The assumption that the payment is bounded also makes it easy to see how
changes in parameters affect the position of the demand curve. Suppose, for example, the
entire distribution of the payment shock is shifted by some constant, so that P is
distributed on [ P + c, P + c] . This might happen, for example, if the bank knows that it
must make a late day payment of size c in addition to the usual uncertainty. In this case,
the entire demand curve shifts to the right. The quantity of reserves demanded at any
given interest rate increases by exactly c.
Another interesting exercise is to suppose that the bank faces more uncertainty about its
end-of-day payment flows, which can be modeled by increasing the support of the
payment shock. To take a specific example, suppose the support changes to
[ P − c, P + c] , which corresponds to a mean-preserving spread in the case of the uniform
distribution. It is not difficult to see that this change will necessarily make the slope of
the downward-sloping part of the demand curve flatter. The effects of other changes,
including changes to the policy regime, are also fairly straightforward to incorporate, as
we show in the sections that follow.
4

If the shock instead had an unbounded distribution, such as the normal distribution used by Whitesell
(2006a) and others, the demand curve would again have this same shape, but would asymptote to the rate rp
and to the horizontal axis without ever intersecting them.



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2.

EXTENSIONS AND ISSUES

In this section, we discuss several extensions of the basic framework that enable it to
address issues that are important to consider in designing a system of monetary policy
implementation. We continue to focus on the current U.S. policy regime. We first look
at factors affecting interest rate volatility, which leads naturally to the study of reserve
maintenance periods. We then discuss the effect of charging fees for daylight credit and,
finally, the differences between large and small banks in the context of the framework.
2.1 INTEREST RATE VOLATILITY
In this subsection we discuss interest rate volatility in the basic framework and how it
relates to the slope of the demand curve in Figure 1. The Central Bank performs daily (or
periodic) open market operations that aim to set the supply of reserves as close as
possible to the target level. This process requires the Open Market Desk to accurately
forecast both reserve demand and changes in the existing supply of reserves due to
autonomous factors such as payments into and out of the Treasury’s account. Forecasting
errors will lead the actual supply to deviate from the target and, hence, will cause the
market rate to differ from target, even if reserve demand is perfectly anticipated.
Figure 3 illustrates the fact that a flatter demand curve is associated with less volatility in
the interest rate, given a particular level of uncertainty associated with autonomous
factors. Suppose that uncertainty about the magnitude of the change in autonomous
factors implies that, after a given open market operation, the total supply of reserves will
be equal to either sL or sH in the figure. With the steeper (blue) demand curve, this
uncertainty about the supply of reserves leads to a relatively wide range of uncertainty
about the market rate. With the flatter (orange) demand curve, in contrast, the variation in
the market rate is smaller. This simple result demonstrates that the slope of the demand
curve, and those policies that affect the slope, are important determinants of the observed
degree of volatility of the interest rate around the target.
As discussed in Section 1.2 above, the slope of the demand curve in the basic framework
depends on the distribution of the late-day payment shock P. The orange line in Figure 3
represents demand under a wider support, that is, a situation where banks face greater
uncertainty about the late day shock. This larger amount of uncertainty will lead to a
flatter demand curve and, hence, lower volatility in the market interest rate due to
forecast errors or unanticipated changes in the supply of reserves.
Central banks generally aim to minimize volatility in their target interest rate. For this
reason, a variety of real-world arrangements have been designed in an attempt to decrease
the slope of the demand curve, at least in the “relevant” region. Perhaps the most
significant of these arrangements is reserve maintenance periods, which we discuss in the
next subsection.

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Figure 3: Interest Rate Volatility
Overnight rate
Supply of reserves
discount 

rate 


Demand for reserves
high 

volatilty 


rH
rL

low volatilty

rL
0

2.2

sL

sH

Nonborrowed
Reserves

RESERVE MAINTENANCE PERIODS

The basic framework can be adapted to study individual days in a reserve maintenance
period. For expositional purposes we study a two-day maintenance period, but the
insights generated here are helpful for understanding the effects of longer maintenance
periods as well. The model for the second day of the period is exactly as above. In this
subsection, we derive the demand for reserve balances on the first day of the period.
Let K denote the average daily requirement, so that the total requirement for the two-day
maintenance period is 2K. A bank’s demand for reserves on the first day of the
maintenance period depends crucially on its belief about what the market interest rate
will be on the second day. The key insight is to realize that banks will try to hold
reserves to satisfy more of the requirement on the day (within the maintenance period) in
which they expect interest rates to be lowest.
Suppose a bank expects the market interest rate on the second day to equal the target rate.
Figure 4 depicts the demand for reserves on the first day under this assumption. To
understand the shape of this demand curve, suppose the interest rate in the market on the
first day is very high, close to the discount rate. Then the bank will want to satisfy as
much of its reserve requirement as possible on the second day, when it expects the rate to
be substantially lower. However, if the bank’s reserve balance after the payment shock is
negative, it will be forced to go borrow at the penalty rate rp to avoid having an overnight
overdraft. As long as the market rate is below the penalty rate, therefore, the bank will
choose a reserve position of at least P. If it chose a position smaller than P, it would be



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certain to need to borrow funds at the end of the day, which cannot be an optimal choice
as long as the market rate is below the penalty rate. 5

Figure 4: First day of a Two-day maintenance period
Overnight rate

rp

total requirement

target
rate

P 0

P

2K+P 2K

2K+P

Nonborrowed
Reserves

For interest rates below rp, but still larger than the target rate, the bank will choose to
hold some “precautionary” reserves to decrease the probability that it will need to borrow
at the penalty rate. This precautionary motive generates the first downward-sloping part
of the demand curve in the figure. As long as the day-one interest rate is above the target
rate, however, the bank will not hold more than P in reserves on the first day. By
holding P , the bank is assured that it will have a positive reserve balance after the lateday payment shock. If the bank were holding more than P on the first day, it could lend
those reserves out at the (relatively high) market rate and meet its requirement by
borrowing reserves on the second day, when the interest rate is expected to be at (lower)
the target, yielding a positive profit. Hence, the first downward-sloping part of the
demand curve must end at P .
Now suppose the first-day interest rate is exactly equal to the target rate. In this case, the
bank expects the rate to be the same on both days and is, therefore, indifferent between
holding reserves on either day for the purpose of meeting requirements. In choosing its
first-day reserve position, the bank will consider the following issues. First, it will
5

Note that Figure 4, like the previous figures, is drawn under the assumption that P is negative. Choosing
a negative reserve position should be interpreted as lending more reserves than the bank begins the day
with and thus incurring a daylight overdraft when the funds are sent.



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choose to hold at least enough reserves to ensure that it will not need to borrow from the
discount window at the end of the first day. In other words, reserve holdings will be at
least as large as the largest possible payment P . The bank is willing to hold more
reserves than P for the purpose of satisfying some of its requirement. However, it wants
to avoid the possibility of over-satisfying the requirement on the first day (that is,
becoming “locked-in”), since it must hold a non-negative quantity of reserves on the
second day. This implies that the bank will not be willing to hold more than the total
requirement (2K) plus the smallest possible payment shock (P) on the first day. (Note that
if P is negative, as drawn in the figure, the amount 2K+ P is less than the total
requirement 2K.) The demand curve is flat between these two points (that is, P and
2K+P), indicating that the bank is indifferent between the various levels of reserves in
this interval.
Finally, suppose the market interest rate on the first day is smaller than the target rate.
Then the bank wants to satisfy most of the requirement the first day, since it expects the
market rate to be higher on the second day. In this case, the bank will hold at least 2K+P
reserves on the first day. If it held any less than this amount, it would be certain to have
some requirement remaining on the second day, which would not be an optimal choice
given that the rate will be higher on the second day. As the interest rate moves farther
below the target rate, the bank will hold more reserves for the usual precautionary
reasons. In this case, the bank is balancing the possibility of being locked-in after the
first day against the possibility of needing to meet some of its requirement on the moreexpensive second day. The larger the difference between the rates on the two days is, the
larger the quantity the bank will choose to hold on the first day. This tradeoff generates
the second downward-sloping part of the demand curve.
The flat portion of the demand curve in Figure 4 can help reduce interest rate volatility on
days prior to the settlement day. As long as movements in autonomous factors are small
enough that the supply of reserves stays in the flat area of the demand curve, interest rate
fluctuations will be minimal. However, it should be noted this demand curve is flat at
whatever interest rate is expected to obtain on the settlement day. Here we have assumed
that rate is equal to the Central Bank’s target. If market participants expect a deviation
from the target on the second day, the demand curve on the first day will reflect that
deviation (see Bartolini, Bertola and Prati (2002) for an analysis of such effects). 6
On the settlement day, the flat portion of the demand curve disappears and the curve
reverts to that in Figure 1. This feature of the model indicates that the market interest rate
is likely to be more volatile on settlement days, which matches observed data. In
practice, however, clearing bands and carryover provisions are typically used in an
attempt to limit this volatility. These provisions have the effect of creating a small range
where the demand curve is flat, or nearly flat, even on a settlement day.
6

Suppose, for example, that banks expect the settlement-day interest rate to be higher than the target. Then
the flat portion of the first-day demand curve would lie at this higher rate. In such a case, implementing the
target rate on the first day becomes more difficult for the Central Bank, since it would need to set reserve
supply on a downward-sloping part of the demand curve instead of on the flat portion. This fact would
tend to make the first-day interest rate more volatile.



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It should be noted that Figure 4 is drawn under the assumption that the reserve
requirement is relatively large. Specifically, 2 K > P − P is assumed to hold, which
ensures that P is less than 2K − P . In other words, the total reserve requirement for the
period is assumed to be larger than the single-day uncertainty about the bank’s reserve
position. If this inequality were reserved, the flat portion of the demand curve would not
exist. In this case, the two downward-sloping parts of the curve would overlap and the
analysis becomes more complicated. In general, reserve maintenance periods are most
useful as a policy tool when the underlying reserve requirements are sufficiently large
relative to end-of-day balance uncertainty.
2.3

EFFECT OF FEES FOR DAYLIGHT CREDIT

All of the figures above were drawn under the assumption that the interest rate charged
on daylight credit is zero, which is a close approximation of current U.S. policy. When
the daylight credit rate is very small relative to the overnight interest rate, a bank’s choice
of (overnight) reserve position will be independent of its anticipated pattern of payment
flows during the day. In this case, reserve demand can be studied without specifying the
pattern of payments during the day and the corresponding usage of daylight credit.
If the interest rate on daylight credit is significant, however, a bank has an extra incentive
to hold reserves overnight, as these reserves help it avoid incurring daylight overdrafts
the following day. 7 In other words, costly daylight credit will tend to increase the
precautionary demand for reserves. In such a situation, daylight credit policy and the
pattern of payments during the day will affect the demand for reserves and the process of
monetary policy implementation.
We can explicitly include daylight credit in the basic framework by adding daytime
payments to the model. Suppose, for example, that each bank makes one payment and
receives one payment during the “early” part of the day (this is in addition to the late-day
payment shock P discussed above). To keep things as simple as possible, suppose that
these two payment flows are of exactly the same size (call this size PD) and that this size
is non-stochastic. However, the order in which these payments occur is random; some
banks will receive the incoming payment before making the outgoing one, while others
will make the outgoing payment before receiving the incoming one. Banks in the latter
category will incur a daylight overdraft.
In terms of the model, let re denote the interest rate on daylight credit and R the level of
reserves chosen by the bank in the interbank market. Let δ denote the time period
between the two payment flows and π the probability that a bank sends the outgoing
payment before receiving the incoming one. Then the bank’s expected cost of daylight
7

We assume that interbank trades settle at the end of the day, so that a bank’s choice of reserve position for
the current day affects the size of its daylight overdrafts on the following day. However, the specific
assumptions made about the timing of settlement are unimportant. As long as interbank trades are 24-hour
loans and the expected pattern of payments is roughly the same on subsequent days, the timing of
settlement has no effect on the analysis.



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credit is π reδ ( PD − R) . This expression shows the relationship between a bank’s
overnight reserve balance and its daylight credit charges. In particular, it shows that an
additional dollar of reserve holdings will decrease the bank’s expected cost of daylight
credit by π reδ .
We think of PD as being large relative to K and P, reflecting the large demand for
daylight credit observed in the data. Therefore, the term (PD – R) will typically be
positive and large in magnitude. If all payments made by one bank are received by
another, the parameter π will be one-half. If, on the other hand, we think of some
daytime payments as going to institutions that are net users of reserves during the day
(CHIPS, etc.), the value of π, and thus the fraction of banks who make a payment before
receiving one, would be larger than one-half.
The analysis here takes the size and timing of payments as given. Several papers have
studied the interesting question of how banks respond to incentives (and to the actions of
other banks) in choosing the timing of their outgoing payments and, hence, their daylight
credit usage. 8 We abstract from such concerns here in order to keep the analysis tractable.
A more complex model might also have multiple rounds of payments, so that a bank’s
reserve position would evolve throughout the day, perhaps randomly. While such an
approach would be necessary for addressing certain questions, the simple approach
presented here is a useful starting point and sufficient for illustrating the important issues.
Figure 5 shows how a bank’s demand for reserves changes when daylight credit is costly.
It is still true that there will be no demand for nonborrowed reserves whenever the market
rate is above the penalty rate rp. The interest rate measured on the vertical axis is (as in
all of our figures) the rate for a 24-hour loan. If the market rate were above the penalty
rate, a bank would prefer to lend out all of its reserves at the (high) market rate and
satisfy its requirements by borrowing from the discount window. By arranging these
loans to settle at approximately the same time on both days, this plan would have no
effect on the bank’s daylight credit usage and hence would generate a pure arbitrage
profit.
It is also still true that whenever the market rate is below the penalty rate the bank will
choose to hold at least K+P reserves, since otherwise it would be certain to need to
borrow after the payment shock is realized in order to meet its requirement. As the figure
shows, the downward-sloping part of the demand curve is flatter when daylight credit is
costly. For any market interest rate below the discount rate, the bank will choose to hold
a higher quantity of reserves because these reserves now have the added benefit of
reducing daylight credit fees.
Rather than decreasing all the way to the horizontal axis as in Figure 1, the demand curve
now becomes flat at the bank’s expected marginal cost of intraday funds, π reδ . As long
as R is smaller than PD, the bank would not be willing to lend out funds at an interest rate
8

See, for example, McAndrews and Rajan (2000) and Bech and Garratt (2003).



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below π reδ because lending out these funds would increase the expected daylight credit
fees the bank would have to pay by more than the interest earned on the loan. For values
of R larger than PD, the bank is holding sufficient reserves to cover all of its intraday
payments and the demand curve drops to the horizontal axis. The “break” in the
horizontal axis indicates that we view PD as being much larger than the other quantities in
the graph.

Figure 5: Effect of Costly Daylight Credit
Overnight rate

rp

target
rate

demand with
positive fee

cost of
credit

demand with
zero fee
0

K+P s1 s2

K+P

Nonborrowed
Reserves
PD

As the figure shows, when daylight credit is costly the level of reserves required to
implement the given target rate is higher (s2 rather than s1 in the diagram). In other
words, costly daylight credit tends to increase the equilibrium level of precautionary
reserve balances. However, given the small costs currently associated with daylight
credit in most countries, this effect will typically be fairly small in practice.
The analysis above assumes a particular form of daylight credit usage; if an overdraft
occurs, the size of the overdraft is constant over time. Alternative assumptions about the
process of daytime payments would lead to slight changes in the figure. Suppose, for
example, that a bank’s daylight overdraft is pyramid-shaped over the course of the day,
building slowly to a peak level and then declining. In this case, the marginal cost of
intraday funds would be decreasing in R, rather than being constant as in the case studied
above. As a result, the portion of the demand curve beyond K + P would be slightly



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downward-sloping instead of flat. However, the qualitative properties of the figure
would be largely unchanged.
2.4 HETEROGENEITY
The analysis above was based on the assumption that all banks are identical, so that the
aggregate demand curve for reserve balances is identical to each individual bank’s
demand curve. Once we derived this individual demand curve, therefore, we could
directly examine how changes in reserve supply affect the market interest rate. We now
ask how the analysis changes when there is explicit heterogeneity among banks. In
particular, we focus on the potential differences between large and small banks. We ask
how such heterogeneity affects the aggregate demand for reserves and the process of
monetary policy implementation in the context of our basic analytical framework. We
also investigate how banks may be affected differently by the process of monetary policy
implementation, and the Central Bank’s choice of framework, depending on their size.
Banks can differ in several dimensions in the framework presented here. Perhaps the
most natural way of capturing differences in bank size is by allowing for heterogeneity in
the magnitude of the reserve requirement. Large banks will tend to have a large deposit
base and, hence, be subject to larger requirements. Other ways in which banks may differ
are the variance of the late-day payment shock they face and the penalty rate they pay
when they need to borrow to make up a deficiency at the end of the day or of a reserve
maintenance period. We address each of these potential sources of heterogeneity below.

Size of Requirements. Suppose that each bank i has a different reserve requirement Ki.
Large banks will have higher values of Ki, and small banks will have lower values. This
type of heterogeneity turns out to have no effect on the analysis above. In particular, the
individual demand curves can be aggregated into the demand curve that would be
generated by a “representative bank” whose requirement is exactly equal to the average
of the individual bank requirements. All of the analysis above then applies equally to the
representative bank and to each individual bank.
To see why this is true, consider a bank’s “precautionary” reserve balance, which we
define to be the difference between its chosen balance Ri and the requirement Ki. The
difference (Ri – Ki) depends on the properties of the payment shock, but not on the size of
the requirement Ki. In other words, suppose we compare two banks that face the same
distribution of the late-day payment shock. Suppose one of the banks has a larger
requirement Ki and will, therefore, hold a higher reserve balance Ri. However, both banks
are facing essentially the same decision problem: choosing a quantity of precautionary
reserves to optimally balance the risk of a reserve deficiency against the risk of being
stuck holding excess reserves. Both banks will, therefore, choose to hold exactly the
same quantity of precautionary reserves (Ri – Ki). As a result, this particular type of
heterogeneity has no effect on bank behavior and the process of monetary policy
implementation in this framework, and all banks are affected equally by the Central
Bank’s choice of framework.



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Adding heterogeneity in reserve requirements does generate an interesting implication for
the distribution of excess reserve holdings across banks. Suppose the banking system is
composed of a relatively small number of large banks and a much larger number of small
banks, as is the case in the U.S. Then, under the assumption that most of these banks face
comparable late-day payment uncertainty, the framework suggests that large and small
banks should hold comparable quantities of precautionary reserves. After the payment
shocks are realized, of course, some banks will end up holding excess reserves and others
will end up needing to borrow. But it will necessarily be the case that the vast majority
of excess reserves in the banking system will, on any given day, be held by small banks,
simply because there are so many more of them. Even if large banks hold the majority of
total reserve balances because of their larger requirements, the framework predicts that
most of the excess reserve balances will be held by small banks. This prediction is
broadly in line with the data for the U.S.

Size of the Payment Shock. Another way in which banks potentially differ from each
other is the distribution of the late-day payment shock they face. Banks with larger and
more complex operations, for example, might be expected to face a larger amount of
uncertainty about their end-of-day reserve position. Of course, such banks tend to have
sophisticated reserve management systems in place. As a result, the end-of-day
uncertainty they face will tend to be much smaller in relative terms, compared to the size
of their operations or their requirements. However, the important variable in the
framework studied here is the absolute size of the uncertainty, not the relative size.
Whether large banks or small banks face more absolute uncertainty is not clear. We now
investigate the effects of introducing heterogeneity in the absolute size of uncertainty
faced by banks into the model.
This type of heterogeneity can be introduced by allowing banks to have different bounds
for the payment shock.9 Suppose that the payment shock for bank i has support [ P i , P i ] ,
with the spread between these bounds being wider for larger banks. It can be shown that
this type of heterogeneity also has no effect on the analysis presented above. In
particular, when the distribution of the payments shock is uniform, the aggregate demand
for reserves is exactly as presented in Figure 1 with the bounds P and P set to the
average values of P i and P i , respectively. The slope of the demand curve is then
determined by the “average” level of uncertainty that banks face. The process of
monetary policy implementation is, therefore, completely unaffected by this type of
heterogeneity.
Having this type of heterogeneity does allow the model to address the question of how
precautionary reserve balances are distributed across banks and how this distribution
responds to changes in the market interest rate. Consider two banks, one that faces more
9

When the distribution of the payment shock is uniform, changing the bounds of the support is equivalent
to changing the variance of the distribution. With more general distributions, this need not be the case.
One could imagine, for instance, that larger banks face a larger support of the shock but, due to their
investment in reserve management capabilities, face a smaller variance. For most of the analysis, the
variance of the distribution plays a more significant role than the support.



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late-day payment uncertainty and one that faces less. The demand curves for each of
these banks are plotted in Figure 6. The curves are scaled as if the two banks had the
same level of requirements, but that is not important. The focus in each case is on the
quantity of precautionary reserves held (that is, the difference between the reserve
balance and the requirement). The figure shows that when the interest rate is high, the
bank facing less uncertainty will hold more precautionary reserves, while the bank facing
more uncertainty will hold more when the interest rate is low. Another way of stating
this result is to say that the bank facing more uncertainty will adjust its reserve holdings
more aggressively in response to changes in the market interest rate. A period of interest
rate volatility would, therefore, be accompanied by large swings in the reserve position of
such banks, and much smaller swings in the reserve position of banks that face less
uncertainty. If we interpret smaller banks as facing less (absolute) uncertainty, this result
would imply that the reserve demand of smaller banks is less sensitive to changes in the
interest rate. Notice that this result obtains even though there are no costs of reserve
management in the model.

Figure 6: The Size of the Payment Shock
Overnight rate
demand with
less uncertainty
rp
high
rate
demand with
greater uncertainty
low
rate

0

K+PH

K+PS

K+PS

K+PH

Ri

Stigma and the Penalty Rate. A third way in which banks might differ from each other is
in the penalty rate they face if they need to borrow to avoid a reserve deficiency. To be
eligible to borrow at the discount window, for example, a bank must establish an
agreement with its reserve bank and post collateral. This fixed cost may lead some
smaller banks to forgo accessing the discount window and instead pay the (higher)
reserve deficiency fee when necessary. Smaller banks may also have difficulty
borrowing in the Fed Funds market late in the day, leading them to pay higher rates or to
face the deficiency fee when hit with a large payment outflow (see Ashcraft, McAndrews



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and Skeie, 2007). In addition, there may be other, internal reasons why different banks
would assign different non-pecuniary costs to borrowing from the discount window.
We can add this type of heterogeneity to the model by assuming that bank i faces an
institution-specific penalty rate rp,i when its reserve balance falls below its requirement.
In this case, aggregating the individual bank demand curves into an aggregate demand for
reserves is slightly more complex than before, but the outcome is qualitatively similar.
The aggregate demand curve will still resemble that in Figure 1, and the slope of this
curve will be based on a representative penalty rate rp. 10 The process of monetary policy
implementation is, therefore, largely unaffected by this type of heterogeneity.
Figure 7 shows how the behavior of individual banks will differ. Smaller banks, which
we think of as facing a higher penalty, will hold more precautionary reserves for any
given interest rate in order to decrease the probability that they will need to borrow. In
the figure, the smaller bank will hold a quantity s2 while the larger bank holds only s1,
even though both face exactly the same uncertainty about their end-of-day balance. As a
result, the distribution of excess reserves will tend to be skewed ever more heavily
toward smaller banks. Notice also that the demand curve of smaller banks will have a
steeper slope, meaning that their reserve demand is less sensitive to changes in the
interest rate.

Figure 7: Heterogeneity in Deficiency Penalties
Overnight rate
rp,2
rp,1
target
rate

demand with
high penalty

demand with
low penalty
R
0

K+P

s1

s2

K+P

10

This representative rate is not a simple average of the individual rates rp,i because, in this case, the
aggregation process is nonlinear.



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3.

ALTERNATIVE SYSTEMS OF MONETARY POLICY IMPLEMENTATION

This section shows how the central ideas of the policy proposals discussed in the body of
the document can be illustrated in the context of the framework developed in this
appendix. Rather than discussing the specific proposals, we focus on those features that
lie within the scope of the basic framework. Some important distinctions between the
various proposals, such as that between reserve requirements and contractual balances, lie
completely outside this scope. Nevertheless, the framework can be used to illustrate the
ways in which each proposal would likely affect the demand for reserves, as well as the
procedure by which the target interest rate would be implemented under each proposal.
In the subsections that follow, we show how the interest rate paid on reserves, both
required and excess, affects the shape of the aggregate demand curve for reserves. We
also describe how the different proposals aim to limit interest rate volatility. While the
figures below are each different from the basic model presented in Figure 1, they all share
the feature that the demand for reserves is generally downward sloping. As we discussed
in Sections 1 and 2, this demand curve can be quite steep, and this steepness makes
implementing a target interest rate difficult because the Central Bank cannot precisely
control the supply of reserve balances. Each of the policy proposals contains elements
that aim to decrease the slope of the demand curve and thereby stabilize the market
interest rate near the target. Some of the proposals rely on reserve maintenance period, as
presented in Section 2.2 above, but others do not.

3.1 PAYING INTEREST ON REQUIRED RESERVE BALANCES
One possible policy would be to keep the basic structure of monetary policy
implementation unchanged, but to pay interest on the reserve balances held by banks that
are used to meet requirements. An important issue that must be decided in this case is
how to determine which part of a bank’s reserve holdings is used to meet requirements
(and hence will earn interest) and which part is considered to be excess. This matters
because the FSRRA authorizes the payment of interest on reserve balances held at the
Fed, but not on vault cash. One approach is to count vault cash toward requirements first.
Under this rule, a bank will only earn interest on the difference between its reserve
requirement and its vault cash holdings. Banks that are currently “unbound,” in the sense
of meeting their entire requirement with vault cash, would earn no interest under this
policy. 11
If we view the level of each bank’s requirement as being fixed, this policy change has no
effect whatsoever on the analysis presented in the previous two sections. The policy
would increase banks’ revenue, but it would have no impact on the decision problem a
11

An alternative approach would be to allow each bank to choose which of its reserves to count toward the
requirement. Under this rule, a bank would elect to apply its reserve balances (rather than vault cash)
toward the requirement first in order to maximize the interest it receives. This approach could have the
effect of removing the opportunity cost of holding additional reserve balances for some institutions, which
would lead to substantial changes in the analysis.



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bank faces. Each bank would continue to choose its precautionary reserve balance (Ri –
Ki) based on the factors described above. The demand curves in the various figures
would be completely unaffected.
In reality, of course, the levels of reserve requirements are not fixed and can be
influenced by banks’ behavior. For example, banks might engage in less reserve
avoidance activity under this policy, resulting in a higher level of required reserves; this
effect may or may not be small. In addition, this policy would introduce an incentive for
banks to economize on vault cash holdings. The effects of this incentive might be worth
studying. However, as described in Section 2.4, changes in the level of requirements do
not affect the decision problem a bank faces when choosing its level of precautionary
reserves. As a result, the process of monetary policy implementation would proceed
almost exactly as described above.

3.2 A CONVENTIONAL SYMMETRIC CORRIDOR
The key features of a corridor system are standing Central Bank facilities that lend to and
accept deposits from commercial banks at fixed interest rates. Figure 8 depicts the
demand curve for nonborrowed reserves under such a system. As in Figure 1, this curve
represents the aggregate demand for reserve balances on the last day of a reserve
maintenance period. The curve looks very similar to that in Figure 1. In particular, there
is no demand for nonborrowed reserve balances if the market interest rate is higher than
the rate at the lending facility. 12 For lower values of the market rate, banks will, on
average, choose to hold the required level of reserves plus some precautionary balances.
This precautionary demand is decreasing in the interest rate for exactly the same reasons
as before. The big change from Figure 1 is that the demand curve now becomes flat at
the deposit rate, rather than at the horizontal axis. If the market rate were below the
deposit rate, each bank’s demand for reserves would effectively be infinite, as they would
try to borrow at the market rate and hold the reserves at the deposit facility overnight,
making a pure profit.
Notice that the width of the downward-sloping part of the demand curve is exactly the
same as in Figure 1; it is again determined by the support of the late-day payment shock.
This fact has an immediate implication for the slope of the demand curve: the presence of
a deposit facility will make the demand curve less steep than before (assuming the
lending facility rate is unchanged). The deposit facility makes holding excess reserves
less costly and, therefore, leads each bank to demand more precautionary reserves. The
lower the market interest rate is, the more important this effect becomes (precisely
because the bank is choosing to hold more reserves). As a result, the demand curve
becomes flatter and a bank’s reserve position will be more responsive to changes in the
market interest rate.

12

This statement assumes that the lending facility is designed in such a way that banks attach no stigma or
other non-pecuniary costs to borrowing from it. It is not clear to what extent converting the discount
window in the U.S. to a lending facility in a corridor system would change the stigma levels banks
perceive.



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However, the slope of the demand curve remains steep enough that a Central Bank will
most likely want to use some additional tool(s) to limit interest rate volatility. In a
corridor system with required reserves, reserve maintenance periods can serve this
purpose. As analyzed in Section 2.2, reserve maintenance periods tend to create a flat
portion of the demand curve near the target rate on non-settlement days. On a settlement
day, however, the demand curve would revert to that in Figure 8, unless some other tools
(such as carryover provisions or clearing bands) are employed.

Figure 8: A Conventional Corridor
Overnight rate

lending 

rate 


target rate
demand for reserves
deposit rate
Required
reserves
0

K+P

target supply

K

K+P

Nonborrowed
Reserves

At the aggregate level, the equilibrium interest rate is determined exactly as before, by
the height of the demand curve at the level of reserve balances supplied by the Central
Bank. Notice that the introduction of a deposit facility creates a floor below which market
interest rate will not fall. In Figure 1, if reserve supply turned out to be unexpectedly
large, the market interest rate could fall all the way to zero. 13 In Figure 8, this cannot
happen; even with a large deviation of reserve supply from the target, the market interest
rate can only fall down to the deposit rate.
In practice, corridor systems are often symmetric, in that the lending and deposit rates are
set an equal distance from the target rate (say, x basis points above and below the target
rate, respectively). In such a case, changing the Central Bank’s target rate effectively
amounts to changing the levels of both the lending and deposit rates, which shifts the
13

While the effective Federal Funds rate rarely deviates from the target by a very large amount, in recent
months there have been many occasions on which the market rate has approached 1 percent or lower during
certain portions of the trading day. The presence of a deposit facility would likely put a floor on the
interest rate for all trades, not just for the effective rate.



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demand curve along with them. The supply of reserves may not need to change much in
order to maintain the new target rate. In fact, in the simple model studied here, the target
level of reserve supply would not change at all when the policy rate changes.

3.3 A NARROW CORRIDOR WITH NO RESERVE REQUIREMENT
Rather than introducing reserve maintenance periods, another way to limit interest rate
volatility in a corridor system is to move both the lending and deposit rates closer to the
target (see Figure 9). As discussed above, narrowing the corridor has two effects on the
level of interest rate volatility. First, the lending and deposit rates create a ceiling and a
floor, respectively, for the market interest rate. Moving these two rates closer together,
therefore, will limit the potential for large deviations from the interest rate target. If, for
example, the lending and deposit rates are both set 25 basis points away from the target,
deviations from the target rate of more than 25 basis points should occur rarely, if at all.

Figure 9: A Narrow Corridor
Overnight rate

lending
rate
target rate

demand for reserves

deposit rate

target supply

P

0

P

Nonborrowed
Reserves

In addition, narrowing the corridor makes the demand curve flatter. The width of the
downward-sloping part of the demand curve is always determined by the support of the
payment shock; it is equal to P – P . When the corridor is narrower, the demand curve
falls by a smaller amount in this range and, hence, has a lower slope. Small deviations of
reserve supply from the target level would thus lead to smaller variations in the interest
rate compared to a wider corridor system as depicted in Figure 8. However, such
deviations might still be large when compared to a non-settlement day in a system with
reserve maintenance periods. If so, the narrow corridor approach could lead to more
small deviations, but fewer large deviations from the target.



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Countries that operate a narrow corridor system with no reserve maintenance period
typically do not have any required reserves. For this reason, Figure 9 is drawn under the
assumption that requirements are set to zero. One consequence of this approach is that it
becomes more likely that unanticipated movements in autonomous factors will leave the
total level of reserves in the system negative. When this happens, some banks must
borrow from the discount window, even if interbank markets are operating well and all
banks are behaving prudently. Having a narrow corridor implies that the penalty paid by
banks in this situation is not unduly large.
3.4 THE “FLOOR” SYSTEM: A CORRIDOR WITH HIGH RESERVE BALANCES
Starting from the corridor system in Figure 9, notice that there is another way in which a
Central Bank could limit the amount of interest-rate volatility that is caused by
unexpected deviations in reserve supply. Suppose the Central Bank were to (i) set the
deposit rate equal to the target interest rate, instead of below it, and (ii) choose reserve
supply so that it intersects the flat part of the demand curve generated by the deposit rate,
as illustrated in Figure 10, rather than intersecting the downward-sloping part as in the
previous figures. Then small, or even large, deviations in reserve supply would have
almost no effect on the market interest rate because the demand curve is perfectly flat in
this region. This approach is called a “floor system” because it relies on the Central Bank
supplying enough reserves to drive the market interest rate down to the “floor” created by
the deposit facility.

Figure 10: A Floor System
Overnight rate
lending
rate

demand for reserves
deposit rate
= policy rate
or

0

P

P

target
supply

target
supply

Nonborrowed
Reserves

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The fact that these supply and demand curves cross at the target rate does not imply that
trades in the interbank market would occur at exactly this rate, of course. A bank would
require a small premium, reflecting transactions costs and credit risk, in order to be
willing to lend out funds rather than simply holding them as (interest-bearing) reserves.
As a result, the measured interest rate in the interbank market would generally be slightly
above the deposit-facility rate. The deposit rate in this system should be referred to as the
policy rate rather than the target rate in order to make this distinction clear.
Compared to all of the systems discussed above, including those with reserve
maintenance periods, the floor system should be the most effective at maintaining the
market interest rate near the target. Recall from Section 2.2 that the systems with reserve
maintenance periods rely on an expectational effect: the flat portion of the demand curve
on a non-settlement day lies at whatever interest rate market participants expect to prevail
on later days. Under a floor system, in contrast, the flat part of the demand curve always
lies at the policy rate chosen by the Central Bank. In addition, the flat portion is very
wide and is the same every day, rather than changing each day in a reserve maintenance
period.
Another unique feature of the floor system is that the quantity of reserves can, to a large
degree, be chosen independently of the interest rate target. This fact is shown clearly in
Figure 10, where the same policy rate is consistent with both a moderate level of reserve
supply and a much larger one. This feature allows the Central Bank to use the supply of
reserves to achieve other objectives, such as changing the amount of broad liquidity in
the economy or affecting the level of daylight overdrafts in the payments system.

3.5 DAILY REQUIREMENTS WITH WIDE CLEARING BANDS
Clearing bands provide another way in which a Central Bank can generate a flat region in
the demand curve for reserves without introducing a reserve maintenance period.
Suppose the Central Bank establishes reserve requirements and operates a symmetric
corridor, as in Figure 8. There is no reserve maintenance period, so the reserve
requirements apply to each day. 14 Assume that interest is paid on required reserve
balances at the target rate. The distinguishing feature of a clearing-band system is that a
bank need not meet this requirement exactly. Instead, it faces no penalty as long as its
final balance falls somewhere within a “clearing band” around the target.
For concreteness, suppose a bank has a reserve requirement K, but with a clearing band
given by the interval [KL,KH]. These bounds might, for example, be set x% below and
above K, respectively. In general, the level of the requirements K is not important in this
type of system; only the upper and lower bounds of the clearing band matter. The bank is
required to hold at least KL reserves each day; if it falls short of this amount it must
borrow the difference at the penalty rate established by the lending facility. The bank is
paid the target interest rate on all of these balances as well as any balances it holds up to
14

These requirements could either be based on the deposits banks hold, as in the current U.S. system, or
could be contractual in nature.



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KH. Any reserve holdings above KH are considered to be “excess” and earn the lower rate
established at the deposit facility.
Figure 11 presents the demand for reserves under this system. We assume the clearing
band is wide enough so that K L + P is less than KH + P. In other words, we assume the
width of the clearing band is greater than the amount of uncertainty the bank faces about
its late-day payments. While narrower bands could also potentially be effective tools for
monetary policy implementation, the benefits of the clearing-band approach are most
clear when the band is sufficiently wide. As shown in the figure, the demand curve for
reserves is flat, at the target interest rate, in between K L + P and KH + P. To see why this
happens, suppose the market rate were equal to the target and ask what quantity of
reserves a bank would choose to hold. The bank would want to (1) hold enough reserves
to ensure that a late-day payment shock will not force it to borrow from the discount
window and (2) hold few enough reserves to ensure that a late-day payment receipt will
not push its reserve balance above the upper bound of the band. The bank will be
indifferent between any level of reserves that ensures these two things, which generates
the flat portion on the demand curve in the figure. 15

Figure 11: Wide Clearing Bands
Overnight rate
lending
rate

demand for reserves
target
rate
deposit
rate

0 KL+P

KL+P

target
supply

R
KH+P

KH+P

15

See Whitesell (2006b) for a similar system based on contractual balances, but where the lower bound KL
is set to zero.



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REFERENCES


Ashcraft, Adam, James McAndrews and David Skeie (2007) “Precautionary reserves and
the interbank market,” mimeo., Federal Reserve Bank of New York.
Bartolini, Leonardo, Guiseppe Bertola and Alessandro Prati (2002) “Day-to-day
monetary policy and the volatility of the federal funds interest rate,” Journal of Money,
Credit and Banking 34, 137–159.
Bech, Morten L. and Rod Garratt (2003) “The intraday liquidity management game”
Journal of Economic Theory 109, 198–219.
Carpenter, Seth and Selva Demiralp (2006) “The liquidity effect in the federal funds
market: evidence from daily open market operations,” Journal of Money, Credit, and
Banking 38, 901-920.
Clouse, James A. and James P. Dow Jr. (1999) “Fixed costs and the behavior of the
federal funds rate,” Journal of Banking & Finance 23, 1015-1029.
Clouse, James A. and James P. Dow Jr. (2002) “A computational model of banks'
optimal reserve management policy,” Journal of Economic Dynamics & Control 26,
1787-1814.
Ennis, Huberto M. and John A. Weinberg (2007) “Interest on reserves and daylight
credit,” Federal Reserve Bank of Richmond Economic Quarterly 93 (Spring) 111-142.
Furfine, Craig H. (2000) “Interbank payments and the daily federal funds rate,” Journal
of Monetary Economics 46, 535-553.
McAndrews, James and Samira Rajan (2000) “The timing and funding of Fedwire funds
transfers” Federal Reserve Bank of New York Richmond Economic Policy Review 6
(July) 17-32.
Poole, William (1968) “Commercial bank reserve management in a stochastic model:
implications for monetary policy,” Journal of Finance 23, 769-791.
Whitesell, William (2006a) “Interest rate corridors and reserves,” Journal of Monetary
Economics 53, 1177-1195.
Whitesell, William (2006b) “Monetary policy implementation without averaging or rate
corridors,” Finance and Economics Discussion Series Paper 2006-22, Federal Reserve
Board.

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