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Do Changes in Mortgage Credit Constraints
Explain the Housing Boom and Bust?
Andra Ghent
University of Wisconsin-Madison

Tipping Points III Symposium
Washington, DC

October 12, 2018

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Introduction
• Significant changes in mortgage credit and home ownership
over past two decades
• Causes of 2000-2007 housing boom still not completely
understood
• Effects of regulatory tightening in the residential mortgage
market during bust unclear
• Declines in home ownership hard to disentangle from changes
in preferences for home ownership, changes in household
formation, etc...

1 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

This Paper
1. Summarize trends in home ownership and mortgage debt over
past two decades
2. Present life cycle model that explores effect of relaxing and
tightening mortgage credit constraint on home ownership and
mortgage debt level
• focus on change in maximum Loan-to-Value (LTV) household
can take on to buy home

Take homes:
1. Relaxation of LTV constraint cannot explain 2000-2007 boom
period data
• in data no increase in age-adjusted US home ownership during
boom period

2. Tightening of LTV constraint can explain some of the decline
in US home ownership in the bust period
2 / 29

US Home Ownership Rate 1994 - 2017
Aggregate and by Income Category

Source: U.S. Census Bureau, Current Population Survey / Housing Vacancy
Survey, July 26, 2018.

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Aging of US Population

Source: Age and Sex Composition: 2010. 2010 Census Briefs, U.S. Census
Bureau.

⇒ Need to look at home ownership rates within age
categories!

4 / 29

US Home Ownership by Age Category

Source: U.S. Census Bureau, Current Population Survey / Housing Vacancy
Survey, July 26, 2018.

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Summary of Home Ownership Patterns

1. Increase in aggregate and age-adjusted home ownership rates
1994-2001
2. Slight decrease in age-adjusted home ownership rates
2001-2007
3. Significant decrease in aggregate and age-adjusted home
ownership rates 2007-2017

6 / 29

US Real Mortgage Debt and Home Prices, 1994-2017

Sources: Federal Reserve Financial Accounts of the United States, FHFA,
FRED, and BLS.

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Can Rising Home Prices Explain Explosion in Debt Levels?
Hypothetical Change in Mortgage Debt for Home Price Growth of 40%

Assume: No increase in down payment size or income

Home Price
LTV
Mortgage Debt
Down Payment

2000
$ 300,000
80%
$ 240,000
$ 60,000

2007
$ 420,000
86%
$ 360,000
$ 60,000

Growth
40%
50%

So, at most, ability to afford same home with rising prices can
explain half the increase in mortgage debt
Adelino, Schoar, and Severino (2018) actually find no change in
CLTV ratios at origination so actual increase caused by decreasing
affordability is likely much smaller
8 / 29

Growth in Mortgage Debt in Boom Broad-Based

Source: Foote, Loewenstein, and Willen (2016).

Growth in Nonprime Securities
Issuance of MBS in $B

Source: SIFMA.

But average income for borrowers of mortgage in PLMBS pools
>100,00$ (Ghent, Hernández-Murillo, and Owyang (2015))
• Subprime / alt-A was a middle-class phenomenon

Take Aways

1. Housing boom period (2000-2007) saw no growth in home
ownership rate other than through demographic change
2. More than doubling of stock of mortgage debt during boom
• Explosion of Nonprime PLMBS market
• Must be due to growth along the intensive margin given home
ownership patterns
• Likely a significant role for home equity extraction after
mortgage origination during boom

3. Significant decline in non-demographic related homeownership
in bust

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Model Overview
• Life cycle / OLG endowment economy
• Households choose:
•
•
•
•
•
•

tenure
house size (if owners)
mortgage type (if owners)
whether to default
consumption
saving

• Equilibrium mortgage rate for each mortgage type sets
expected PV of mortgage equal to mortgage amount
• Sources of risk:
• home values (idiosyncratic)
• income (idiosyncratic)
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Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Overview
• Exogenous risk-free rate, r
• Exogenous relative price of housing, q
• Housing stock depreciates at a rate of δ every period
• Home owners must pay δ every period in which they own to
maintain the property
• Financial intermediaries must pay a cost χ (percent of home
value) to rehabilitate any home acquired through foreclosure

13 / 29

Households
• Born at age 0 and live for at most J periods
• start life with no assets and as renters

• “Work” for the first JRET periods of life
• Each period face a probability πj of dying
• Bequest motive
• Face stochastic income risk
• income follows a Markov Process

• If home owner, face stochastic home values

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Households
Tenure Choice

• Each period, chooses whether to own or rent
• If chooses to rent, no home size choice
• rents a home of size h1

• If chooses to own, buys a home of size h2 (h2 > h1 ) or h3
(h3 > h2 )
• cannot buy a home of size h1

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Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Households
Tenure Choice

• Felicity depends on tenure
• allow for the possibility that there is a utility premium from
owning

• Can transition in any period between owning and renting

16 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Households
Home Values

• Use same mechanism as Corbae and Quintin (2015) to
capture home price volatility
• Each period while an owner, there is a probability λ that the
home will change in value
• home of size h2 will stay size h2 with probability 1 − 2λ, will
increase to size h3 with probability λ, and will decrease to size
h1 with probability λ
• home of size h3 will stay size h3 with probability 1 − λ and will
decrease to size h2 with probability λ
• owner-occupied home of size h1 will stay size h1 with
probability 1 − λ and will increase to size h2 with probability λ

• Rental homes do not change size (always size h1 )
17 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Households
Mortgage Choices

• Two ways to finance home ownership:
1. Traditional Mortgages (TRADs):
• require down payment of νTRAD % of the home value
• term is T periods
• payments are calculated such that the mortgage is fully
amortizing over T periods
• carry interest rate rTRAD

2. Low Down Payment (LDP) loans:
• require down payment of just νLDP % of home value
• term is T periods
• payments are calculated such that the mortgage is fully
amortizing over T periods
• carry interest rate rLDP

18 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Households
Mortgage Choices

• No refinancing
• keeps computation tractable

• Can terminate the mortgage in any period by either
• defaulting, or
• prepaying

• If defaults, loses the home and must rent for that period
• Prepays by selling the home
• pays selling cost ρ

19 / 29

Financial Intermediaries
• Accepts household savings and makes mortgage loans
• Earns the exogenously given rate r on savings
• Pays a servicing cost, φ, on mortgages it holds
• Holds a stock of housing capital which it can rent out at rate
R per unit or sell to households as owner-occupied housing
• Incurs the maintenance cost δ on its housing stock
• Incurs a cost χqh of rehabilitating housing units it acquires
through foreclosure
• In equilibrium, it must make zero profits
• =⇒ R = rq + δ

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Equilibrium
• Equilibrium mortgage interest rates, rTRAD and rLDP :
• mortgage interest rate that makes the expected present value
of the mortgage equal to the amount of the mortgage
• lender discounts expected cash flows by r + φ

• No closed form solution to this problem
• Solve numerically:
• inner loop solves household optimization problem for each
value of state variable
• outer loop for mortgage interest rates

21 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Parameterization
Demographics

• Period corresponds to 3 years
• Household ‘born’ at age 25
• Household lives to at most 85 chronological years of age
(J = 20)
• Household ‘retires’ at age 64 (JRET = 13)
• Survival rates taken from Arias et al. (2008)

22 / 29

Parameterization
Income

• Assume that the income process during working years follows
an AR(1) process:
yt = ρyt −1 + γ1 aget + γ2 aget2 + ε t

(1)

where ε t has variance σε2

• Estimate (1) using triennial PSID data on earnings from 1967
to 1992
• Approximate (1) with a three state Markov chain using the
approach of Tauchen and Hussey (1991)
• After retirement, labor income is set to 60% of income in the
last working year following Cocco, Gomes, and Maenhout
(2005) and Yao and Zhang (2005)

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Parameterization
Preferences: Felicity Function

• Felicity function follows
u (c, h, H ) = ψ ln c + (1 − ψ) ln h

• Set ψ to 0.76 implying that renters spend 24% of their
consumption expenditure on housing (Davis and
Ortalo-Magné, 2011)

24 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Parameterization
Housing Costs

• Set χ, foreclosure rehabilitation costs, to 0.25 (consistent with
Campbell, Giglio, and Pathak, 2011)
• Set T , mortgage term, to 10 such that mortgages have 30
year terms
• Set vTRAD = 0.2 such that TRADs require a 20% down
payment
• Set r , risk-free rate, to 0.12
• Set ρ, selling-costs, to 8% as in Cocco (2005)
25 / 29

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Parameterization
Housing Costs

• Use the following parameters to calibrate the model to certain
characteristics in the data
•
•
•
•
•

λ: probability of an idiosyncratic house price shock
house sizes, h1 , h2 , and h3
mortgage servicing cost, φ
q: relative price of housing
δ: per period depreciation rate on housing

26 / 29

Steady State Equilibria
Moment
Home Ownership
Low Income
Mid Income
High Income
Under 35
35-44
45-54
55-65
65+
Loan-to-Income
Share LDPs
TRAD Mtg Rate
NDP Mtg Rate
Avg. 30-year
Mtg Rate
Foreclosure Rate

2001
68.0%

Data
2007
67.8%

2016
63.7%

42%
68%
76%
81%
81%
182%

41%
67%
75%
80%
80%
241%

35%
59%
70%
75%
80%
230%

4.97%

4.34%

1.65%

no LDP
71.3%
30%
83%
92%
31%
70%
81%
86%
76%
208%
5.27%
5.27%

Model
νLDP = 0.1
71.5%
30%
83%
92%
31%
71%
81%
86%
76%
207%
2.2%
5.27%
5.93%
5.28%

νLDP = 0.0
72.5%
30%
83%
98%
37%
70%
81%
86%
76%
199%
12.0%
5.27%
7.08%
5.33%

1.29%

1.31%

1.41%

Notes: 1) Data sources are US Census CPS / Housing Vacancy Survey, Federal
Reserve Consumer Finance Survey, and Federal Reserve Bank of St. Louis.

Squaring the Model with the Data
Relaxing LTV constraint raises home ownership rate for young,
high-income households
• HHs that cannot come up with a down payment but want to
smooth consumption
• Reduces average debt ratios slightly
If relaxation of LTV constraint caused the boom, we would have
seen an increase in the home ownership rate, especially young HHs
Model is consistent with tightening of LTV constraint during bust
causing a decline in home ownership
• Consistent with empirical evidence of Duca and Rosenthal
(1994) and Gete and Reher (forthcoming) regarding effect of
credit constraints on home ownership

Introduction

Empirical Facts

Model

Parameterization

Results

Conclusions

Empirical Facts:
1. No increase in age-adjusted home ownership rate over boom
2. Doubling of real residential mortgage debt during boom
3. Significant increase in home ownership rate in years leading up
to the boom
4. Significant decline in home ownership rate during bust
Model of tenure choice predicts that main effect of relaxation of
LTV constraint is an increase in home ownership
Main beneficiaries of relaxation of LTV constraints in model are
high-income young households

29 / 29