On the Economics of Subprime Lending

US mortgage markets have evolved radically in recent years. An important part of the change has been the rise of the subprime market, characterized by loans with high default rates, dominance by specialized subprime lenders rather than full-service lenders, and little coverage by the secondary mortgage market. In this paper, we examine these and other stylized facts with standard tools used by financial economists to describe market structure in other contexts. We use three models to examine market structure: an option-based approach to mortgage pricing in which we argue that subprime options are different from prime options, causing different contracts and prices; and two models based on asymmetric information–one with asymmetry between borrowers and lenders, and one with the asymmetry between lenders and the secondary market. In both of the asymmetric-information models, investors set up incentives for borrowers or loan sellers to reveal information, primarily through costs of rejection.     

Interest-only and principal-only mortgage strips as interest-rate contingent claims

Interest-only (IO) and principal-only (PO) mortgage strips are valued in a stochastic interest-rate environment. The prepayment rate of the underlying mortgages is affected by two considerations not present in the pure financially rational model: (1) The property owner's holding period is assumed to follow a Gamma distribution, resulting in the possibility of prepayment due to the sale of the property (i.e., prepayment that is too early based on market interest rates); and (2) borrowers are assumed to face heterogeneous transaction costs related to refinancing the existing mortgage, and delay refinancing when market conditions make it optimal to do so (refinancing too late). Properties of IO/PO strips are identified by the finite difference method.     

FHA vs. Subprime Mortgage Originations: Is FHA the Answer to Subprime Lending?

We analyze originations of mortgages guaranteed by the Federal Housing Administration (FHA) and of subprime mortgages—loans that dominate the non-prime mortgage market for riskier borrowers. Using home purchase and refinance loans data for 2005, we estimate that a sizeable number of borrowers who got subprime loans would have qualified for FHA loans, implying a potential net flow of borrowers from subprime to FHA, especially for refinance loans at a rate of about 30%. Also, consistent with the FHA’s modernization proposal to increase its loan limits, we find that increasing the limits on FHA loans could help to attract borrowers, mostly of home purchase loans, who are likely to be constrained by the lower-priced house limits. Our findings are generally in line with the recent increased flow of mortgages to FHA, and suggest that FHA loans could be the answer to the current subprime lending crisis.     

Benefits to Homeowners from Mortgage Portfolios Retained by Fannie Mae and Freddie Mac

Mortgage investing is the domain of financial intermediaries, such as Fannie Mae and Freddie Mac, who possess specialized knowledge and experienced analytic teams. Capital is channeled to homeowner/borrowers at lower cost through such entities. As the demand for mortgage borrowing outstrips aggregate domestic saving (which is currently negative) foreign sources of capital should become even more significant. Foreign capital can be channeled efficiently into the U.S. mortgage market by Fannie and Freddie. Their debt has the highest credit standing and their risk management ability has been demonstrated by their enormous retained portfolios of mortgages.     

The Neighborhood Distribution of Subprime Mortgage Lending

Subprime lending in the residential mortgage market, characterized by relatively high credit risk and interest rates or fees, has developed over the past decade into a prominent segment of the market (Temkin, 2000). Recent research indicates that there is geographical concentration of subprime mortgages in Census tracts where there are high concentrations of low-income and minority households. The growth in subprime lending represents an expansion in the supply of mortgage credit among households who do not meet prime market underwriting standards. Nonetheless, its apparent concentration in minority and lower income neighborhoods has generated concerns that these households may not be obtaining equal opportunity in the prime mortgage market. Such lending may undermine revitalization to the extent that it is associated with so-called predatory practices.     

GSEs,Mortgage Rates,and the Long-Run Effects of Mortgage Securitization

Our paper compares mortgage securitization undertaken by government-sponsored enterprises (GSEs) with that undertaken by private firms, with an emphasis on how each type of mortgage securitization affects mortgage rates. We build a model illustrating that market structure, government sponsorship, and the characteristics of the mortgages securitized are all important determinants of mortgage rates. We find that GSEs generally—but not always—lower mortgage rates, particularly when the GSEs behave competitively, because the GSEs implicit government backing allows them to sell securities without the credit enhancements needed in the private sector. Using our simulation model, we demonstrate that when mortgages eligible for purchase by the GSEs have characteristics similar to other mortgages, the GSEs implicit government-backing generates differences in mortgage rates similar to those currently observed in the mortgage market (which range between zero and fifty basis points). However, if the mortgages purchased by GSEs are less costly to originate and securitize, and if the GSEs behave competitively, then the simulated spread in mortgage rates can be much larger than that observed in the data.     

The impact of securitization on the expansion of subprime credit

This paper investigates the relationship between securitization activity and the extension of subprime credit. The analysis is motivated by two sets of compelling empirical facts. First, the origination of subprime mortgages exploded between the years 2003 and 2005. Second, the securitization of subprime loans increased substantially over the same time period, driven primarily by the five largest independent broker/dealer investment banks. We argue that the relative shift in the securitization activity of investment banks was driven by forces exogenous to factors impacting lending decisions in the primary mortgage market and resulted in lower ZIP code denial rates, higher subprime origination rates, and higher subsequent default rates. Consistent with recent findings in the literature, we provide evidence that the increased securitization activity of investment banks reduced lenders' incentives to carefully screen borrowers.     

Fixed-Rate Endowment Mortgage and Mortgage Indemnity Valuation

We use a contingent claims framework for valuing the the default and prepayment embedded options in certain British fixed-rate endowment mortgages, with a (capped) mortgage indemnity guarantee (MIG). This methodology provides a template for the borrower, lender, and insurer to compare mortgage terms, including the fairness of contract rates, arrangement fees, prepayment penalties, any MIG premiums required, and co-insurance exposure. With empirical inputs, this model may eventually be useful as a mark-to-value proxy for all parties, as expected parameters change (especially interest rate and house price levels, and expected future volatilities), for purposes of determining valued added accounting, appropriate reserves, and indeed for setting premiums and business drivers. Fixed-rate endowment mortgages differ from fixed-rate repayment mortgages primarily because, in the event of early termination, the amount owed by the borrower is a function of the evolution of the term structure of interest rates, whereas for a repayment mortgage it is pre-determined. We compare endownment and repayment mortgages for different levels of loan-to-value ratios, interest rate and house price volatilities.     

Predatory lending and the subprime crisis

We measure the effect of a 2006 antipredatory pilot program in Chicago on mortgage default rates to test whether predatory lending was a key element in fueling the subprime crisis. Under the program, risky borrowers or risky mortgage contracts or both triggered review sessions by housing counselors who shared their findings with the state regulator. The pilot program cut market activity in half, largely through the exit of lenders specializing in risky loans and through a decline in the share of subprime borrowers. Our results suggest that predatory lending practices contributed to high mortgage default rates among subprime borrowers, raising them by about a third.     

Subprime Lenders and Mortgage Market Completion

Without a subprime market, some borrowers by virtue of poor credit history, unstable income, and other characteristics are unable to qualify for a mortgage. With a subprime market, there is a more complete credit supply schedule with the market pricing for poorer credit quality in the mortgage rate. By completing the capital market, subprime lenders reduce borrowing constraints. The result is a social welfare gain. Low-credit applicants otherwise denied funding are able to qualify by paying higher interest rates in exchange for offering more equity or lower loan-to-value ratios. This prediction is consistent with the subprime applicants financing or refinancing their mortgages at relatively low loan-to-value ratios.     

Performance of residential mortgages in low and moderate-income neighborhoods

This paper presents the first data on performance of mortgages on residences located in lowand moderate-income neighborhoods of U.S. cities. It provides new data on delinquencies and foreclosure provided by a sample of lenders who are members of the National Association of Affordable Housing Lenders and who have lending programs established pursuant to the Community Reinvestment Act.Sample mortgages on multifamily dwellings perform comparably with national sample data, whereas sample mortgages on single-family mortgages perform much better than comparable national sample data.The findings of this paper demonstrate clearly that lending programs in lowand moderate-income neighborhoods can be viable. The findings do not, however, help to settle the issue as the racial or gender discrimination in mortgage origination.This paper is based on Performance Analysis of Community Reinvestment Programs, prepared by the athors for the Woodstock Institute, Chicago, IL.     

Optimal Loan Interest Rate Contract Design

This paper analyzes optimal loan interest rate contracts under conditions of risky, symmetric information for one-period (static) and multi-period (dynamic) models. The optimal loan interest rate depends upon the volatility of, and co-variation among the market interest rate, borrower collateral, and borrower income, as well as the time horizon and the risk preferences of lenders and borrowers. For a risk-averse borrower with stochastic collateral, variable interest rate contracts are, in general, Pareto optimal. For plausible assumptions, the optimal loan interest rate for the multi-period model often exhibits muted responses to changes in market interest rates, making fixed rate loans a reasonable approximation for the optimal loan. Hence, in the absence of optimal contracts, long-term (short-term) borrowers tend to prefer fixed rate (variable) contracts.     

Mortgage Prepayment and Default Behavior with Embedded Forward Contract Risks in China’s Housing Market

Most condominiums in China are sold forward on a pre-sale market, where purchasers and developers transact on an underlying property that is not yet completed. During the pre-sale period home buyers face a significant forward contract risk. However, home buyers can borrow mortgages from banks so that they can effectively share the forward contract risk with banks. This explains the phenomenon of irregularly high early-stage default and prepayment rates observed in residential mortgage lending in China, where there are few, if any, financial incentives for mortgage borrowers to exercise either put or call options. Mortgages collateralized by forward housing assets are riskier than are those with underlying assets traded on the spot market. However, currently Chinese mortgage banks charge the same rate to all mortgage borrowers. This inefficiency in risk sharing between mortgage borrowers’ groups in the forward and spot housing markets leads to mispricing in secondary mortgage sales and mortgage-backed security trading.     

Cointegration and causal relations in mortgage and capital markets

In years past, credit rationing resulted in the primary mortgage market being segmented from national capital markets. Some research suggests that the deregulation of depository institutions in the early 1980s along with the exponential growth in the secondary mortgage market, has resulted in a primary mortgage market more fully integrated with national capital markets. This study employs Granger Causality to test primary and secondary mortgage market segmentation. Our findings support the conclusion that causality is unidirectional from the treasury market to the primary and secondary mortgage market. The results also indicate that mortgage market speed of adjustment increased significantly by the end of the decade.     

The inefficiency of refinancing: Why prepayment penalties are good for risky borrowers

This paper provides a theoretical analysis of the efficiency of prepayment penalties in a dynamic competitive lending model with risky borrowers and costly default. When considering improvements in the borrower's creditworthiness as one of the reasons for refinancing mortgages, we show that refinancing penalties can be welfare improving and that they can be particularly beneficial to riskier borrowers in the form of lower mortgage rates, reduced defaults, and increased availability of credit. Thus, a high concentration of prepayment penalties among the riskiest borrowers can be an outcome of efficient equilibrium in a mortgage market. We also provide empirical evidence that is consistent with the key predictions of our model.     

Risk versus Demographics in Subprime Mortgage Lending: Evidence from Three Connecticut Cities

This paper analyzes patterns in subprime residential mortgage lending using 2006 Home Mortgage Act Disclosure data for the cities of Bridgeport, New Haven and Waterbury, Connecticut. The analysis applies models presented in earlier research and has the objective of assessing the relative importance of demographic versus risk factors in subprime mortgage lending decisions. Regression equations are estimated for census tracts and individual borrowers and include demographic variables and property risk measures. The results find race and ethnicity to be significant determinants of subprime lending in the borrower equations that include the full set of risk measures. Neighborhood educational levels are found to have an inverse and often significant association with subprime mortgage loans. Property risk measures present mixed results regarding their significance in subprime lending, suggesting that risk may have played less of a role in loan originations in 2006 than it did in earlier studies.     

Borrower Self-Selection,Underwriting Costs,and Subprime Mortgage Credit Supply

In the U.S., households participate in two very different types of credit markets. Personal lending is characterized by continuous risk-based pricing in which lenders offer households a continuous distribution of borrowing possibilities based on estimates of their creditworthiness. This contrasts sharply with mortgage markets where lenders specialize in specific risk categories of borrowers and mortgage supply is stepwise linear. The contrast between continuous lending for personal loans and discrete lending by specialized lenders for mortgage credit has led to concerns regarding the efficiency and equity of mortgage lending. This paper sheds both theoretical and empirical light on the differences in the two credit markets. The theory section demonstrates why, in a perfectly competitive credit market where all lenders have the same underwriting technology, mortgage credit supply curves are stepwise linear and lenders specialize in prime or subprime lending. The empirical section then provides evidence that borrowers are being effectively sorted based on risk characteristics by the market.     

Government intervention in the mortgage market: A study of anti-redlining regulations

This paper addresses the question of whether economic incentives exist for mortgage lenders to avoid or to minimize mortgage originations in neighborhoods inhabited primarily by low-income racial minorities. The Option Pricing Model is utilized to determine what mortgage borrower characteristics affect the market value of the mortgage contracts. It is found that existing laws do not enable mortgage lenders to vary either origination prices or mortgage terms so as to adjust for differences in the market values of mortgages. As a result, incentives are created for both the mortgage lender and the mortgage insurer to avoid originations and underwritings in areas with relatively high default probabilities. Various changes in mortgage lending regulations are suggested to eliminate these incentives, and the effects of alternative programs to subsidize mortgage borrowers with relatively high default probabilities are considered.     

The “Rent-To-Own” mortgage and prepayment risk

The most important risk factor in the mortgage and mortgage-backed security market has been prepayment risk. Various innovations have arisen to deal with it but none hedge it fully. The Rent-To-Own (RTO) mortgage discussed here is a mortgage instrument that reduces or even reverses prepayment risk. It does so by creating an incentive structure within the framework of the mortgage contract that penalizes prepayment when interest rates are low and rewards it when interest rates are high. This is the opposite of standard mortgages. The RTO incentive structure is based on a unique buyout feature. Borrowers who want to buy out the financial interest of the lender may do so whenever they want, but the buyout price is a negative function of the market interest rates prevailing currently, that is, at the time of the buyout. Hence the lower these rates, the higher the buyout price. Other advantages of the RTO mortgage are also described.     

Villains or scapegoats? The role of subprime borrowers in driving the U.S. housing boom

An expansion in mortgage credit to subprime borrowers is widely believed to have been a principal driver of the 2002-2006 U.S. house price boom. By contrast, this paper documents a robust, negative correlation between the growth in the share of purchase mortgages to subprime borrowers and house price appreciation at the county-level during this time. Using two different instrumental variables approaches, we also establish causal evidence that house price appreciation lowered the share of purchase loans to subprime borrowers. Further analysis using micro-level credit bureau data shows that higher house price appreciation reduced the transition rate into first-time homeownership for subprime individuals. Finally, the paper documents that subprime borrowers did not play a significant role in the increased speculative activity and underwriting fraud that the literature has linked directly to the housing boom. Taken together, these results are more consistent with subprime borrowers being priced out of housing boom markets rather than inflating prices in those markets.