Optimal Sharing of Interest‐Rate Risk in Mortgage Contracts: The Effects of Potential Prepayment and Default

Much of the literature on the economics of mortgage markets has studied the fixed vs. adjustable‐rate mortgage choice made by individual borrowers. However, to decide if the outcome of such a choice is efficient or approximately so, it is necessary to explore the question of optimal risk‐sharing in mortgage contracts. But because only a small literature has studied this question, more research is clearly warranted. The present article helps fill this gap by developing a simplified version of Arvan and Brueckner's model, using it to characterize optimal contracts in the absence of mortgage termination, and then exploring how termination via prepayment or default affects optimal risk‐sharing. The broad conclusion of the analysis is that potential mortgage termination makes higher risk exposure for borrowers optimal.     

Pricing Mortgage-Backed Securities: Integrating Optimal Call and Empirical Models of Prepayment

Residential mortgage borrowers frequently appear to behave suboptimally with respect to their mortgage prepayment options. Many borrowers fail to exercise even well-into-the-money options while others prepay when the call option is out-of-the-money. To account for these apparently suboptimal prepayments, the recent trend in mortgage-backed securities research has been away from optimal call valuation models, in which the decision to exercise is determined endoge-nously, in favor of models in which prepayment behavior is exogenously specified based on empirical estimation. This paper develops a rational model of mortgage prepayment which incorporates both types of "non-optimal" prepayment and retains endogenous call. This enables the model to disentangle and compare the separate effects of the interest rate call, impeded by transaction costs, and of non-interest-rate driven prepayment. In addition, by recognizing heterogenous borrower transaction costs, the model presents a way to account more precisely for the varying prepayment lags associated with well-into-the-money call options and to account for the phenomenon of "burnout" within a mortgage pool. The paper includes an empirical test of the unbiasedness of the integrated pricing model by comparing simulated prices from our theoretical model to observed prices on traded Fannie Mae and GNMA securities.     

Commercial Mortgage Pricing with Unobservable Borrower Default Costs

This paper develops a pricing model for commercial real estate mortgage debt that recognizes the influence of default transaction costs on the borrower's default decision. These costs are heterogeneous across borrowers and largely un-observable to the lender/investor at the time of origination or loan purchase. A recognition of these unobservable costs can explain why borrower default decisions may differ from those predicted by "ruthless" mortgage-default pricing models. We address the determinants of default choice and timing by replacing sharp default boundaries found in the ruthless models with "fuzzy" boundaries that account for investor uncertainty with respect to evaluating borrower default decisions. To implement our model, we estimate probabilities of default as a junction of time and net equity in the property. Then, given that default occurs, loss severities are modeled based on expected property value recovery net of foreclosure costs and time until the asset is actually sold. Under reasonable parameter value choices, resulting Monte Carlo simulations produce numerical mortgage price estimates as well as component default frequency and severity levels that realistically reflect default premiums and loss levels observed in the marketplace.     

Mortgage Borrower Repayment Behavior: A Microeconomic Analysis with Canadian Adjustable Rate Mortgage Data

In this paper we estimate a model of mortgage borrower behavior using micro-level data on Canadian borrowers with rollover mortgages—a form of adjustable-rate mortgage. Our results suggest that the probability of default rises with a decrease in housing equity and an increase in the mortgage contract rate; however the size of these changes is relatively small. They also show that partial prepayment is sensitive to fluctuations in the rates of return from investing in housing versus other assets. For the United States experience, our results suggest that, relative to fixed-rate mortgage borrowers, adjustable-rate mortgage borrowers are more likely to default and less likely to prepay.     

The Impact of Second Loans on Subprime Mortgage Defaults

An estimated 12.6% of primary mortgage loans were simultaneously originated with a second loan from 2004 until 2008, although relatively little is known about how the presence of such subordinate loans affects the default decisions of borrowers. We use a novel data series of loan servicing records from 2002 until 2010 to identify such borrowers and find evidence that the default behavior of these borrowers significantly differs from borrowers without second loans. Estimating a discrete‐time proportional odds hazard model, we find borrowers with a second loan were 62.7% more likely to default each month on their primary loan when conditioning alone on the attributes of the primary loan. However, borrowers of second loans were 58.3% less likely to default on their primary loan as compared to single‐loan borrowers with equivalent current combined attributes (i.e., loan‐to‐value, balance and interest rate). We hypothesize and provide empirical evidence that this occurs because borrowers with second loans have the option to sequentially default on each loan since subordinate lenders will not pursue foreclosure if borrowers have insufficient equity. Lenders of defaulted subordinate debt may revisit their decision to foreclose in the future after housing markets start to recover, thus prompting a new round of foreclosures.     

Unobservable Risks in Mortgage Contract Choice

This study proposes a lifetime utility maximization model where borrowers choose optimal mortgage bundles including mortgage type, loan‐to‐value and loan size to maximize their allocation of limited budgets between housing and nonhousing consumptions. The model predicts that the mortgage bundle choices by borrowers of different income and risk attributes explain significant variations in the ex post default risks of the borrowers. The empirical tests using sampled mortgages pooled in nonagency residential mortgage backed securities support the hypothesis that the optimal choice of mortgage bundles reveals hidden risk factors of borrowers, which, if ignored, could lead to misjudgment of ex post default of borrowers.     

Choice of Mortgage Contracts: Evidence from the Survey of Consumer Finances

This study revisits the empirical question of the determinants of the choice between fixed‐ and adjustable‐rate mortgages using data from the Survey of Consumer Finances that overcome some of the data limitations in previous studies. The results from a logit model of mortgage choice indicate that pricing variables and affordability are important considerations. We also find that factors, such as mobility expectations, income volatility and attitudes toward financial risk largely influence mortgage choice, with more risk‐averse borrowers preferring fixed‐rate mortgages. For households that are less risk averse, the mortgage type choice decision is less sensitive to pricing variables and income volatility, and affordability factors are not significant. These findings provide empirical support that underscores the importance of attitudes toward risks in mortgage choice.     

Are Adjustable‐Rate Mortgage Borrowers Borrowing Constrained?

Past research argues that changes in adjustable‐rate mortgage (ARM) payments may lead households to cut back on consumption. These outcomes are more likely if ARM borrowers are borrowing constrained, and we show in this article that ARM borrowers exhibit attitudes toward borrowing and behavior that are consistent with being borrowing constrained. Although the demographic and financial characteristics of ARM and fixed‐rate mortgage (FRM) borrowers are somewhat similar, ARM borrowers differ from FRM borrowers in their uses of credit and attitudes toward it. In addition, we find the consumption growth of households with an ARM is more sensitive to past income than the consumption growth of other households, suggesting the ARM borrowers may be subject to borrowing constraints that hinder their ability to smooth consumption.     

Credit History and the FHA–Conventional Choice

Models explaining whether households choose conventional or FHA mortgage financing typically use differential insurance premiums, loan-to-value (LTV) and payment-to-income underwriting standards, and local economic conditions to explain household behavior. Using a large and geographically diverse sample, we expand the standard choice model by including measures of borrower credit history. We find that the ability of a homebuyer to avoid credit problems is an important part of the FHA–conventional choice. In addition, credit scores of FHA borrowers are worse on average than those of conventional borrowers, but as LTV increases credit scores of conventional borrowers deteriorate.     

The Borrower's Perceived Risk in Mortgage Choice

We investigate how borrowers perceive the risk in the adjustable rate mortgage (ARM) versus fixed rate mortgage (FRM) choice. We develop a mortgage choice model where the coefficient on the long‐term bond risk premium is conditional on the borrower's perceived risk. We show that the perceived risk fluctuates over time according to the short‐term interest rate level and housing market conditions. We find that when the short‐term rate level is high (low), the borrowers perceive low (high) risk of a short‐term rate rise, thus opting for ARMs (FRMs). Also, during a down housing market they become more risk‐averse perceiving higher risk in choosing ARMs. The perceived risk level alters the borrowers’ sensitivity to the long‐term bond risk premium.     

Do Riskier Borrowers Borrow More?

Conventional wisdom in the mortgage industry holds that loan-to-value (LTV) ratios are positively correlated with mortgage default rates. However, not all empirical studies of mortgage loan performance support this view. This paper offers a theoretical signaling model of why the correlation between LTV ratios and default risk is contingent upon the default costs of the borrower. Specifically, the model proposes that when default costs are high there exists a separating equilibrium in which risky borrowers will self-select into lower LTV loans to reduce the probability of facing a costly default, while safe borrowers will self-select into higher LTV loans as a signal of their enhanced creditworthiness. This adverse selection process gives rise to the possibility of higher default probabilities for lower LTV loans. Conversely, when default costs are low the conventional result, in which risky borrowers select higher LTV loans than safe borrowers, is obtained. Empirical results, based on a sample of 859 single-family residential mortgage loans drawn from the portfolio of a national mortgage lender, are consistent with the separating equilibria predicted by the model.     

Mortgage Insurance Adoption in the Netherlands

Individuals tend to underinsure on low probability, high consequence risks. Using a survey data set from a unique institutional context, we provide an assessment of the underinsurance puzzle by studying mortgage insurance adoption among Dutch homeowners. The results indicate that the demand for mortgage insurance is affected by risk exposure, type of mortgage lender, and the involvement of financial advisors. We document that wealthier and younger mortgagors are more likely to insure. However, locus of control, house price expectations, and precautionary savings are not related to insurance demand. Finally, we find evidence that borrower (over)confidence negatively affects the likelihood that insurance is bought.     

Estimating Borrower Mobility from Observed Prepayments

This article describes a method used to estimate parameters describing the mobility of borrowers choosing fixed-rate mortgages. Using a mortgage valuation model that predicts prepayments contingent upon parameters describing the distribution of expected tenure in the home, the average mobility of borrowers can be estimated from observed prepayment behavior. This article estimates the mobility of borrowers who chose fixed-rate mortgages before 1980 and borrowers who chose similar mortgages in the second half of the 1980s, when adjustable-rate mortgages were widely available. The empirical results support the claim that the average mobility of fixed-rate borrowers has declined.     

Movers and Shuckers: Interdependent Prepayment Decisions

We model competing risks of mortgage termination where the borrower faces a repeated choice to continue to pay, refinance the loan, move or default. Most previous empirical work on mortgage prepayment has ignored the distinction between prepayments triggered by refinancing and moving, combining them into a single prepayment rate. We show that financial considerations are the primary drivers of the refinance choice while homeowner characteristics have more influence on the move decision. We demonstrate that these differences are statistically significant and that combining these two distinct choices into a single measure of prepayment shifts coefficients toward zero and produces inaccurate predictions of aggregate termination rates. For example, a combined model underestimates the effect of the market price of the loan on refinancing; it misses entirely the opposite effects of borrower income on moving and refinancing. Our results suggest that existing prepayment models are inconsistent predictors of mobility-driven prepayment and underestimate the effect of market conditions and borrower characteristics on refinancing and housing decisions. Our findings have great significance to mortgage investors because mobility-driven prepayments are likely to be a more significant source of prepayments in thenext decade.     

The Conditional Probability of Foreclosure: An Empirical Analysis of Conventional Mortgage Loan Defaults

This paper analyzes the factors affecting the conditional probability that defaulted residential mortgage loans will foreclose. We analyze a large national sample of conventional loans, which have been in default at least once during the 1988 to 1994 period. For such loans, lenders and borrowers either individually or jointly make choices which lead to the following outcomes: (1) resumption of payments, (2) termination by prepayment, or (3) foreclosure. Our estimates of a logit model indicate that termination option values and local area economic and housing market conditions affect default resolution probabilities. Perhaps more importantly, simulations using the logit model indicate that the efficiency of the default resolution process may be substantially improved by legal and regulatory reforms.     

Thy Neighbor’s Mortgage: Does Living in a Subprime Neighborhood Affect One’s Probability of Default?

This article focuses on the potential externalities associated with subprime mortgage origination activity. Specifically, we examine whether negative spillover effects from subprime mortgage originations result in higher default rates in the surrounding area. Our empirical analysis controls for loan characteristics, house price changes and alternative loan products. Our results indicate that, after controlling for these characteristics, the concentration of subprime lending in a neighborhood does not lead to greater default risks for surrounding borrowers. However, we do find that more aggressive mortgage products (such as hybrid adjustable rate mortgages and low/no‐documentation loans) had significant negative spillovers on other borrowers. Stated differently, the aggressive alternative mortgage designs were more toxic to the housing and mortgage market than previously believed.     

Borrower Credit and the Valuation of Mortgage-Backed Securities

We study the valuation of mortgage-backed securities when borrowers may have to refinance at premium rates because of their credit. The optimal refinancing strategy often results in prepayment being delayed significantly relative to traditional models. Furthermore, mortgage values can exceed par by much more than the cost of refinancing. Applying the model to an extensive sample of mortgage-backed security prices, we find that the implied credit spreads that match these prices closely parallel borrowers' actual spreads at the origination of the mortgage. These results suggest that models that incorporate borrower credit into the analysis may provide a promising alternative to the reduced-form prepayment models widely used in practice.     

Relocation Opportunities and Mortgage Default

This paper presents a theoretical model of residential mortgage default when borrowers face beneficial as well as costly relocation opportunities. It amplifies and extends previous work by providing explicit conditions leading to default. The model also establishes when a borrower's relocation decision and default decision are dependent and when they are not.
A central result is that there is a range of book equity wherein the decision to default is not determined solely by the current level of equity or the borrower's ability to continue the mortgage payments. Rather, various costs and benefits, both tangible and intangible, enter into the decision. Specific conditions are identified that lead to relocation without default, default and relocation, and no default or relocation. The effects of changes in the variables upon default probability are presented.
Assuming that the borrower does not wish to retain ownership in the property, the model also predicts whether an individual borrower will choose prepayment or default when a relocation is made. The choice depends on the value of the relocation opportunity faced by the borrower, as well as financial variables such as house value, mortgage balance, and transaction costs. This finding suggests that existing empirical analyses of default may have omitted explanatory variables.     

Differential Access to and Pricing of Home Mortgages: 2004 through 2009

This article documents trends and drivers of the residential mortgage market during the years 2004 through 2009, specifically focusing on the access to and pricing of mortgages originated by African‐American and Hispanic borrowers, and by borrowers living in low‐income and minority communities. Our analysis relies on a rich set of proprietary data that allow more expanded insights than can be obtained from the Home Mortgage Disclosure Act (HMDA) alone. We show that access to mortgage credit increased between 2004 and 2006 for the borrowers we focus on in our study and declined dramatically thereafter. Trends in access to credit were driven primarily by the changing credit mix of mortgage applicants and secondarily by the replacement of the Federal Housing Administration (FHA) for subprime as the dominant mode of nonprime originations and tighter underwriting standards. Throughout our entire period of study, these borrowers also consistently paid higher prices for their mortgages; however, the extent of this differential varied considerably over time and across groups. These pricing trends were driven primarily by changes in the FHA and subprime shares as well as by the market's increasingly aggressive pricing of credit risk.     

How Subprime Borrowers and Mortgage Brokers Shared the Pie

We develop an equilibrium model for origination fees charged by mortgage brokers and show how the equilibrium fee distribution depends on borrowers' valuation for their loans and their information about fees. We use noncrossing quantile regressions and data from a large subprime lender to estimate conditional fee distributions. Given the fee distribution, we identify the distributions of borrower valuations and informedness. The level of informedness is higher for larger loans and in better educated neighborhoods. We quantify the fraction of the surplus from the mortgage that goes to the broker, and how it decreases as the borrower becomes more informed.