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Federal Reserve
Bank of Dallas

VOL. 13, NO. 8 • JUNE 2018

Economic
Letter
Smaller Banks Less Able to
Withstand Flattening Yield Curve
by Pavel Kapinos and Alex Musatov

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ABSTRACT: For the overall
U.S. banking system, the
effect on profitability of
yield-curve flattening—the
lowering of the difference
between the yields of shortand long-term debt—lasts
about a year and is relatively
small. After the first year,
the impact on large banks’
profitability becomes positive;
for smaller institutions, it
stays negative and becomes
larger. Recent yield-curve
flattening is likely to more
strongly affect smaller banks,
reducing their profitability.

A

n analytical and forecasting
mainstay, the yield curve has
been routinely used to forecast a
variety of economic outcomes, including
recessions.1 The yield curve refers to the
rate at which debt interest rates change
from shorter to longer maturities. Usually,
short-term rates are lower than those of
longer maturities.
Low short-term interest rates over a
protracted period and a diminishing yieldcurve slope—the result of a narrowing
“term spread” between short- and longterm rates—have motivated academics,
policymakers and analysts to reexamine
the yield curve’s effect on macroeconomic
and financial variables.
An analysis shows that the link between
the term spread and banks’ profitability is
alive and well, though its strength varies
by bank size.

Banks and the Yield Curve
One way banks earn profits involves
maturity transformation, taking in deposits and lending funds for longer terms,
typically at higher rates. A flattening yield
curve may be signaling an impending
recession that will complicate a bank’s
ability to conduct maturity transformation
profitably, raising broader concerns about
the outlook for U.S. banks’ profitability
and stability.

Although a yield curve can be constructed for any cash-generating debt instrument available with multiple maturities,
the most widely used yield curve relies on
Treasury securities’ yields because U.S.
government debt has virtually no default
risk and is actively traded in secondary
markets.
A closely monitored characteristic of the
yield curve is its slope, or the term spread.
Although the term spread can be calculated between any pair of maturities—or
even as a weighted average of various
pairs—it is conventionally estimated as the
difference between the yield on 10-year
Treasury notes and three-month Treasury
bills. The difference reflects the premium demanded by investors for bearing
additional long-term risk, as well as their
expectations about the future path of interest rates on short-term Treasuries.
Long-term interest rates are normally
higher than short-term rates, in part due
to the liquidity premium associated with
holding securities of longer maturities.
The yield curve, therefore, typically slopes
upward and the term spread is positive. A
flat curve indicates that short- and longterm Treasuries offer the same rates. A
downward-sloping, “inverted” curve
almost always portends a recession—
investors expect future short-term rates
to decrease relative to current levels in

Economic Letter
CHART

1

Short-Term Rates Generally Drive Term Spread
Treasury Yields

Percentage points
16

10-year Treasury constant maturity rate
3-month Treasury constant maturity rate

12
8
4
0

1984

1988

1992

1996

2000

2004

2008

2012

2016

Term Spread

Percentage points
5

10-year rate minus 3-month rate

4
3
2
1
0
-1
1984

1988

1992

1996

2000

2004

2008

2012

2016

NOTE: Shaded areas denote National Bureau of Economic Research-defined recessions.
SOURCE: Federal Reserve Bank of St. Louis FRED database.

CHART

2

Term Spread, Bank Profitability

Net Interest Margin Tends to Move in Unison
for Banks of Differing Sizes

Percentage points*

All banks
Banks with average assets greater than $15B
Banks with average assets between $1B and $15B
Banks with average assets under $1B

5.7
5.2
4.7
4.2
3.7
3.2

2.7
1984

1988

1992

1996

2000

2004

2008

2012

2016

*Quarterly data, annualized; not seasonally adjusted.
NOTES: Shaded areas denote National Bureau of Economic Research-defined recessions.
SOURCE: Federal Reserve Bank of St. Louis FRED database.

response to Federal Reserve rate-cutting
aimed at averting a downturn.
Nominal, or stated, yields on Treasuries
have generally declined for more than

2

for 10-year and three-month instruments
generally move in tandem, the shorter end
of the yield curve is normally more volatile because the Federal Reserve typically
affects economic activity through shortterm rates. Hence, shifts in the slope are
more likely driven by changes in threemonth yields.
One exception to this rule occurred
when short-term rates reached the zero
lower bound following the Great Recession
of 2007–09. During subsequent years, the
Federal Reserve was widely perceived as
conducting monetary policy through longer-term rates by purchasing longer-term
Treasuries and mortgage-backed debt and
issuing forward guidance regarding the
future conduct of monetary policy. The
term spread, thus, reflected the unconventional monetary policy during that period.
The term spread has plunged multiple
times since the 1980s, but it dipped into
negative territory in only three instances—each time accurately presaging a
recession. As the macroeconomic outlook
improved, the yield curve steepened. More
recently, the term spread has gradually
declined but remained positive.2

three decades while the slope of the curve
has fluctuated, reflecting investors’ changing perceptions of future macroeconomic
conditions (Chart 1). Although the yields

Maturity transformation is banks’ principal economic activity.3 Given that banks
pay short-term rates on deposits and
receive long-term rates on loans, their
profitability is sensitive to the difference
between the two. A wider term spread (or a
steeper yield curve) should benefit banks’
bottom lines.
The best measure of bank profits linked
to yield-curve movement is the net interest
margin (NIM). It is calculated as the difference between a bank’s interest income
and interest expense, normalized by the
average size of its interest-earning assets.
The aggregate NIM for U.S. banks peaked
in 1994 and has generally declined since
then, reaching a historical low in fourth
quarter 2015.4
In theory, the portion of bank profits
derived from interest-rate-sensitive activities should reflect changes in the term
spread. In practice, the relationship can be
difficult to demonstrate using static econometric methods, and some attempts have
produced mixed and even counterintuitive
results in advanced economies.5, 6

Economic Letter • Federal Reserve Bank of Dallas • June 2018

Economic Letter
When grouped by size, banks in all
groups find their net interest margins
generally move in the same direction, but
consistent differences in NIM levels arise
between groups of various sizes (Chart 2).
Banks with smaller average earning assets
(less than $1 billion) report higher relative
profitability from interest-sensitive activities, though their outperformance vis-à-vis
larger peers (those with assets greater than
$15 billion) has narrowed over time.
The NIM for smaller banks was 140 basis
points (a basis point equals 0.01 percentage points) higher than for the largest
banks in 1984—when collection of these
data began—but the difference narrowed
to less than 100 basis points in 2017, primarily due to a decline in the profitability
of smaller institutions.

CHART

Effect of 100-Basis-Point Term-Spread Decrease

3

Varies by Bank Size
U.S. Banks with Average Assets
Exceeding $15 Billion

All U.S. Banks

Basis points

Basis points
8
6
4
2
0
-2
-4

10.5
8.5
6.5
4.5
2.5
0.5
-1.5
-3.5
0

2

4

6

8

10

12

0

8

10

U.S. Banks with Average Assets Less
than $1 Billion

12

Basis points
1.5

-0.5

-0.5

-2.5

-2.5

-4.5

-4.5

-6.5
-8.5

6

U.S. Banks with Average
Assets of $1 Billion to $15 Billion
1.5

Disentangling the effects of a changing
term spread on NIM is inherently difficult
because both variables evolve dynamically. Thus, it’s not useful to look at a correlation coefficient between the two variables
or estimate a simple regression model of
NIM on the term spread because the statistical strength of the relationship may
depend on the variables’ joint exposure to
a common factor such as business-cycle
conditions.
Moreover, a one-period variation in the
term spread may affect NIM with a lag,
another aspect of the dynamic relationship
between them. Controlling for exposure to
common drivers helps isolate the effect of
the term spread on NIM.
A macroeconomic time-series model
that studies the joint dynamic evolution of NIM, real gross domestic product
growth, its deflator inflation rate and the
term spread provides a more complete
view.7 This method takes into account the
dynamic relationships between all variables and traces the effects of a one-time
change in the term spread. In other words,
the model accounts for the interplay
between all the variables and then teases
out the effect of the term spread on bank
profitability.
Chart 3 presents the responses of several
NIM measures over three years to a onetime, 100-basis-point decrease in the term
spread, corresponding to a flattening of
the yield curve, as depicted by the model.8

4

Quarters since change in term spread

Basis points

Net Interest Margin Modeling

2

Quarters since change in term spread

-6.5
0

2

4

6

8

10

12

-8.5

Quarters since change in term spread

0

2

4

6

8

10

12

Quarters since change in term spread

95% confidence Interval

Mean response

NOTES: The charts show the impact on net interest margin of a one-time 100-basis-point reduction.
SOURCES: Federal Reserve Bank of St. Louis FRED database; authors’ calculations.

The top left panel suggests that the
response is indeed negative but small
during the first six quarters, significant
only during the first couple of quarters
and insignificant thereafter. When the
yield curve flattens, the NIM shrinks for
multiple quarters.
The top right panel indicates that the
overall shape of the response is primarily driven by the largest banks. For entities with more than $15 billion in assets,
the response stays marginally negative for
the first five quarters and becomes significantly positive after 10. These large banks
appear to move in the direction opposite of
the one predicted by theory at the longer
time horizons.
The picture is different for smaller
banks. Among banks with assets between
$1 billion and $15 billion (bottom left panel), the response to the term-spread shock
remains negative over the entire three-year

period, increasing over time yet remaining
statistically insignificant. Among banks
with less than $1 billion in assets (bottom
right panel), the chart shows a sizable and
consistently negative NIM response to the
term-spread shock that remains negative
and significant over the entire three-year
horizon.9

Differing Asset Bases, Impacts
The relationship between the slope
of the yield cur ve and bank profitability remains very much intact once
multiperiod effects and institutional
size are accounted for. The continued
flattening of the Treasury yield curve
will likely diminish the smaller banks’
net interest margins. Margins likely
will remain largely unaffected among
midsize institutions and will potentially
improve among the largest banks in the
longer term.

Economic Letter • Federal Reserve Bank of Dallas • June 2018

3

Economic Letter

Large banks’ relative insensitivity to the
slope of the yield curve may reflect more
diversified portfolios of earning assets.
Loans, which constitute almost 70 percent
of assets for many midsize banks, compose
less than 50 percent of assets at the largest
institutions. In turn, large banks hold higher percentages of trading assets—securities, including debt instruments—which
respond to changes in the term spread
differently and insulate the banks’ income
statements from variances in interest rates
and spreads.
Smaller banks have a more limited
asset base and generally focus on higheryielding loans, which tend to reprice faster
than deposit rates when the yield curve is
steepening and longer-term rates rise.
Thus, small banks’ NIMs widen in an era
of rising rates more significantly and for a
longer period.
Further research may uncover additional factors that explain the differential
responses of small and large banks to
changes in the slope of the yield curve.
Kapinos is a research economist and
Musatov is a specialist in the Supervisory
Risk and Surveillance Department at the
Federal Reserve Bank of Dallas.

Notes
See “Predicting U.S. Recessions: Financial Variables
as Leading Indicators,” by Arturo Estrella and Frederic S.
Mishkin, Review of Economics and Statistics, MIT Press,
vol. 80, no. 1, 1998, pp. 45–61. For an ongoing evaluation
of this relationship, see “Yield Curve and Predicted GDP
Growth, April 2018,” Federal Reserve Bank of Cleveland, accessed April 23, 2018, www.clevelandfed.org/our-research/
indicators-and-data/yield-curve-and-gdp-growth.aspx.
1

10-Year Treasury Constant Maturity Minus 3-Month Treasury Constant Maturity [T10Y3M], FRED database, Federal
Reserve Bank of St. Louis, Feb. 15, 2018, accessed April 24,
2018, https://fred.stlouisfed.org/series/T10Y3M.
2

3
Banks derive profits from many other activities, such as
liquidity transformation, credit transformation and payment
services.

For a comprehensive discussion of factors behind net
interest margin decline, see “Why Are Net Interest Margins
of Large Banks So Compressed?” by Francisco B. Covas,
Marcelo Rezende and Cindy M. Vojtech, FEDS Notes,
Federal Reserve Board of Governors, Oct. 5, 2015, accessed
April 24, 2018, www.federalreserve.gov/econresdata/notes/
feds-notes/2015/why-are-net-interest-margins-of-largebanks-so-compressed-20151005.html.
4

“Interest Rate Risk and Bank Net Interest Margins,” by
William B. English, BIS Quarterly Review, Bank for International Settlements, December 2002, www.bis.org/publ/
qtrpdf/r_qt0212g.pdf.

5

summary of recent studies related to bank profitability in
a low-rate environment, see “Low Interest Rates and Bank
Profits,” by Katherine Di Lucido, Anna Kovner and Samantha
Zeller, Liberty Street Economics, Federal Reserve Bank of
New York, June 21, 2017, accessed April 24, 2018, http://
libertystreeteconomics.newyorkfed.org/2017/06/lowinterest-rates-and-bank-profits.html.
7
Technical details of the estimation framework are available
upon request. The results are robust to alternative measures
of business-cycle conditions, such as the change in the
unemployment rate and core personal consumption expenditures (PCE) inflation or other definitions of the term spread.
8
“Estimation and Inference of Impulse Responses by Local
Projections,” by Oscar Jorda, American Economic Review,
vol. 95, no. 1, 2005, pp. 161–82. The results hold in the
time series from Haver Analytics that start in first quarter
1991 and group banks in three categories: smaller than $50
billion, $50 billion–$500 billion and over $500 billion.
9
The framework we use here imposes symmetry between
positive and negative 100-basis-point increases. Allowing
for asymmetries and nonlinearities in Jorda’s approach
(see note 8), the responses of large banks’ net interest
margins are largely symmetric, whereas most of the small
banks’ responses are driven by the episodes of negative
term-spread shocks that correspond to the flattening or
inversion of the yield curve and are disproportionately larger
as those shocks increase in size.

6
A number of studies have suggested that the absolute level
of interest rates—not just the term spread—affects bank
profitability and have posited possible explanations. For a

Federal Reserve Bank of Dallas

Economic Letter

Marc P. Giannoni, Senior Vice President and Director of Research

is published by the Federal Reserve Bank of Dallas. The views expressed are those of
the authors and should not be attributed to the Federal Reserve Bank of Dallas or the
Federal Reserve System.

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