Hedging GNMA Mortgage-Backed Securities with T-Note Futures: Dynamic versus Static Hedging

This article proposes a dynamic hedging model for Government National Association Mortgage-Backed Securities (GNMA MBSs) that is free of the drawbacks associated with the static hedging strategies currently used. The simultaneity bias of the regression approach is dealt with by modeling the joint distribution of price changes of GNMA MBSs and 10-year Treasury-note futures. Error correction (EC) terms from cointegrating relationships are included in the conditional mean equations to preserve the long-term equilibrium relationship of the two markets. The time-varying variance–covariance structure of the two markets is modeled via a version of the bivariate generalized autoregressive conditionally heteroskedastic model (bivariate GARCH), which assures that the time-varying variance–covariance matrix is positive semidefinite for all time periods. This dynamic error-correction GARCH model is estimated using daily data on six different coupon GNMA MBSs. Dynamic cross-hedge ratios are obtained from the time-varying variance–covariance matrix using the 10-year Treasury-note futures contract as the hedging instrument. These ratios are evaluated in terms of both overall risk reduction and expected utility maximization. There is overwhelming evidence that dynamic hedge ratios are superior to static ones even when transaction costs are incorporated into the analysis. This conclusion holds for all six different coupon GNMA MBSs under investigation.     

An Arbitrage-Free Estimate of Prepayment Option Prices in Fixed-Rate GNMA Mortgage-Backed Securities

In an efficient market, the no-arbitrage condition implies that the price difference between any two assets must be the market value of all differences in their cash flows. We use this logic to deduce the price of the prepayment option embedded in fixed-rate Government National Mortgage Association (GNMA) mortgage-backed securities. The option price equals the difference between an observed GNMA price and the cost of a synthetic, nonprepayable GNMA constructed from the least expensive portfolio of Treasury securities that exactly replicates the promised GNMA cash flow stream, assuming prepayment is precluded. We regress the option prices on variables found significant in previous prepayment studies, finding that five key regressors explain more than 90% of the prepayment option value in pooled time-series cross-sectional analysis. We also show that the time value of the prepayment option calculated by our method displays a pattern similar to that produced by the Black-Scholes (1973) option pricing model. An additional empirical result is the existence of negative option prices and negative time value of the option prices. We attribute these to the fact that homeowners sometimes exercise their prepayment options when they are out-of-the-money, and to refinancing transaction costs. Our method is independent of assumptions regarding interest rate processes and the homeowner's prepayment behavior, and it provides a benchmark for testing theoretical prepayment models.     

Interest-Rate Volatility, Basis Risk and Heteroscedasticity in Hedging Mortgages

This paper investigates the validity of the OLS regression to estimate the hedge ratio for mortgages (GNMA) and provides alternative methodologies. In particular, this paper is concerned with the variance structure (conditional and unconditional heteroscedasticities) and the misspecification (nonlinearities) of the simple linear regression model for direct as well as cross-hedging. Using data on spot prices of GNMA and futures prices of GNMAs and T-bills for the period September 1979 to January 1985, we show that there exists significant heteroscedasticity particularly for cross-hedging, and nonlinearity between cash and futures prices for direct as well as cross-hedging. Alternative hedge ratio estimates are provided using the Box-Cox transformation model and an autoregressive conditional heteroscedastic (ARCH) Model.     

Mean Reversions in GNMA Returns

The random-walk hypothesis is tested in the prices of mortgage-backed securities traded in the secondary market. Using the variance ratio test, the random-walk hypothesis is rejected for the daily GNMA bond return. We identify two components in the return series: a systematic component reflecting the market pricing on the expected information, and a noise term that represents the pricing on the unexpected information. After adjusting for the impact of bid-ask spread and thin trading on the price quotations, the evidence suggests that the short-horizon, weekly realized return, being dominated by the negative serial correlation of the random component, exhibits a mean-reverting process. However, it is also found that the noise term demonstrates significant positive serial correlation for holding periods of over two weeks. Thus, for longer-term returns, the realized return exhibits positive dependence. The implication is that the price of GNMA bonds did not react to unexpected information in a rational fashion in that the adjustment process is not instantaneous.     

Hedging Forward Mortgage Loan Commitments: The Option of Futures and a Future for Options

The purpose of this paper is to analyze theoretically the problem of how mortgage lending institutions assume the interest rate risks inherent in the granting of fixed-rate mortgage loan commitments.
Two approaches to hedge this risk are analyzed. First, the use of the GNMA futures market is evaluated from the standpoint of how it might be used to hedge against mortgage commitment risks. Secondly, the use of an appropriate pricing model—the Black-Scholes option pricing model—is offered as a proxy for establishing the market value of a fixed-rate mortgage commitment. This model is extended and empirically estimated for several hypothetical environments.
The paper demonstrates a basic flaw in the GNMA futures market as a hedge against mortgage commitments. Once this is established, the use of the options pricing approach is offered as a more rational approach for hedging these risks.     

Martingale property in bond futures return including volatility spillover effect from bank bill futures

This paper analyses the time series properties of the daily return from the ten-year bond futures contracts traded on the Sydney Futures Exchange (SFE), together with the transmission of volatility from other interest rate futures contracts. The methodology relies on appropriate modelling of the conditional heteroscedasticity observed in the futures price change series. It is then evident that the volatility spillover effect exists from the short-term bank bill futures to the ten-year bond futures and not the other way. This suggests that the traders attempt to make inferences from price movements in other interest rate futures contracts which ultimately impinge upon the price movement in the bond futures contracts. It is indicative of the expectation theory of the term structure.The author is Lecturer in Finance in the School of Finance and Economics, University of Technology, Sydney.     

Interest Rate Risk, Residential Mortgages and Financial Futures Markets

Residential mortgage markets in both the United States and Canada have recently been dominated by instruments such as variable-rate and short-term rollover mortgages which require borrowers to assume a greater burden of interest rate risk. An outstanding question is whether this approach to risk allocation is Pareto optimal or whether there are other more effective methods of dealing with the risk created by interest rate volatility. This study examines the potential for shifting this risk from the mortgage market to the financial futures market. After considering the rationale for expecting that neither mortgage borrowers nor lenders wish to absorb the high levels of risk present in the existing financial environment, this study discusses the hedging of interest rate risk through financial futures markets. Empirical tests are then performed to evaluate the effectiveness of U.S. futures markets for hedging positions from the U.S. mortgage market. These results indicate that the interest rate risk inherent in residential mortgages can be substantially shifted through one or more positions in the existing futures contracts and long-term, fixed-rate mortgages may still be financially feasible under conditions of interest rate volatility.     

Elective Mortgage Prepayment: Termination and Curtailment

Mortgage-prepayment risk underlies the structuring of mortgage-backed derivative securities, such as tranched real estate mortgage investment conduits. This prepayment comes either from mortgage termination or from curtailment, where the borrower retains the existing mortgage and prepays a portion. There are differences in cash flows from the two types of prepayment. In termination, the loan disappears from a pool, and the scheduled payment to investors in the pool is reduced. In curtailment, the loan survives, and the scheduled payment is unchanged but the term is reduced. There are implications for structuring mortgages and derivative securities. The prepayment decision is embedded in an in-tertemporal household utility maximization framework where choices are made between refinancing, making the regular payment, default or curtailment. Empirical results are presented for Government National Mortgage Association (GNMA) pools, and an algorithm is presented that separates the termination and curtailment components, facilitating the development of derivative securities.     

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.     

应用上海燃料油期货套保航空燃油的可行性分析

我国的航空公司(航油贸易公司)采购航空燃油大多以新加坡的MOPS价格作为签订进口贸易合同的计价基准,因此大多在新加坡的场外衍生品市场进行套期保值交易。文章从实证角度研究了应用上海燃料油期货对航油进行套期保值的可行性。通过相关性分析、ADF检验、协整检验等,验证了新加坡航油现货价格与上海燃料油期货价格具有很高的相关性,并存在长期稳定的关系。从套保比率看,上海燃料油期货的套保比率高于WTI原油期货,这是因为上海燃料油期货价格的波动性低于WTI原油期货合约的价格波动性。从套保绩效检验看,WTI原油期货优于上海燃料油期货,即在同种合约时间长度下,使用WTI原油期货合约套保比使用上海燃料油期货合约套保降低风险的程度更大。实证研究表明,运用上海燃料油期货为新加坡航油现货进行套期保值可以取得一定效果,从而为航空公司规避航油市场价格波动风险提供保障。     

Rates of Return on GNMA Securities: The Cost of Mortgage Funds

This paper examines rates of return earned on GNMA securities over the period January 1971 through June 1978. We find that over this period the mean monthly return on GNMAs was greater than the mean return on long-term government bonds and slightly greater than the mean return on high-grade corporate bonds. However, in neither case was the difference statistically significant. Thus, based on this evidence, it is not possible to conclude that the cost of acquiring funds to finance single-family housing purchases through the GNMA program exceeded the cost of acquiring funds by the U.S. treasury or financially-strong corporations.     

Mortgage Choice: What's the Point?

This article shows that, in the presence of transaction costs payable by borrowers on refinancing, it is possible to construct a separating equilibrium in which borrowers with differing mobility select fixed rate mortgages (FRMs) with different combinations of coupon rate and points. We also show that, in the absence of such costs, no such equilibrium is possible. This provides a possible explanation for the large menus of FRMs typically encountered by potential borrowers, and suggests that the menu available at the time of origination should be an important predictor of future prepayment. We numerically implement the model, developing the first contingent claims mortgage valuation algorithm that can quantify the effect of self-selection on real contracts in a realistic interest rate setting. The algorithm allows investors to account for self-selection when valuing mortgages and mortgage-backed securities. It also, for the first time, allows lenders to determine the optimal points/coupon rate schedule to offer to a specified set of potential borrowers, given the current level of interest rates.     

Determinants of GNMA Mortgage Prices

This paper contrasts three different arbitrage-based models for the pricing of GNMA securities, and analyzes the effect of different assumptions about the call policy pursued by the issuers of the underlying mortgages. Both the nature of the interest-rate uncertainty captured by the model and the assumed call policy have a major effect on the yield differentials predicted between GNMA securities and Treasury Bonds.     

Measurement of the Spreads Between Yields on Various Mortgage Contracts and Treasury Securities

Spreads between yields on different mortgage instruments and comparable maturity portfolios of Treasury securities have been computed and compared with quoted yields over the 1974–82 period for three different mortgage instruments: GNMA pass-throughs, FHLMC participation certificates, and conventional mortgage commitments. The methodology explicitly accounts for the expected timing of the payments on the mortgages and thus avoids the cash-flow timing problems noted in the literature.
Between late 1978 and 1981, the computed spreads rose by 30 to 40 basis points relative to those customarily quoted (the internal rate of return on a mortgage, assuming a twelve-year life, less the yield on near-par ten-year Treasuries). This increase can be attributed to the rise in the level of interest rates (the compounding error in quoted mortgage yields is larger at higher levels of rates) and the change in the slope of the yield curve from flat to downward sloping (the twelve-year prepayment date assumed in the computation of quoted GNMA and FHLMC PC yields seems to be too long).     

部分发达国家利率期货发展路径及对我国的启示

随着中国人民银行在1996年建立全国统一的拆借市场以及尝试国债市场化的发行,我国拉开了利率市场化的序幕。利率市场化加速推进的过程中,利率风险将逐步加大,利率期货作为有效的风险管理工具,已成为世界成熟金融市场最重要的金融衍生工具。本文研究了美国、英国和日本等发达国家利率期货的发展路径,并从利率现货市场培育、利率期货合约设计、政府监管和自律监管等三方面得到发展我国利率期货的启示。     

Hedging spot fuel oil in Singapore: Will the new SIMEX contract succeed?

We assess SIMEX's new market for fuel oil futures by examining its effectiveness in hedging a cash fuel oil position in Singapore. We find that the SIMEX contract can eliminate about two-thirds of the volatility of a Singapore cash position and is many times more effective than a cross-hedge constructed with overseas contracts. Given its potential usefulness as a hedging tool for the regional petroleum industry, we anticipate that the new contract will be a success.We are grateful to Mobil (New York) for making the Platt oil price data available to us and to Jim Bovenage specifically for accessing the data for us.     

美国房地产抵押贷款证券化及其启示

在分析美国房地产抵押贷款证券化发展历程及其主要特点的基础上，对推进我国房地产抵押贷款证券化提出了几点建议。     

Fixed‐Term Contracts: Short‐Term Blessings or Long‐Term Scars? Empirical Findings from the Netherlands 1980–2000

Using a comprehensive longitudinal dataset of prime‐age Dutch workers over the period 1980–2000, we examine how a previously held job with a fixed‐term contract influences both the likelihood and the duration of a future spell of unemployment. Analyses show that Dutch workers with fixed‐term contracts experience higher risks of future unemployment and have no shorter spells of unemployment compared to workers with regular contracts. Results also reveal that swifter employment re‐entries among men with fixed‐term contracts can be explained by their job search efforts before unemployment. Our study (partly) invalidates theoretical positions that claim that fixed‐term contracts foster employment security by shortening unemployment durations; suggesting that fixed‐term contracts are a short‐term blessing that could end, for some workers, in a recurrent unemployment trap.     

油价理论回顾与展望

从国际原油交易定价入手,回顾和述评了关于"持有成本套利"和"现货溢价"的两种理论脉络和实证结论,结合原油期货合约具有实物商品和金融投资工具双重属性,讨论了从交易者行为入手,研究原油期货定价机制的主要思路和成果.强调后续研究应该坚持从考察交易者行为的角度来发掘油价形成的原因,把资本市场的变化、实体市场和期货市场同时纳入原油期货价格形成的研究中,才可能真正创造性地揭示油价决定和变化的内在规律,而对交易者行为"理性化"或"非理性化"的界定和争论可能直接影响未来对油价研究的结论     

The Effect of Refinancing Costs and Market Imperfections on the Optimal Call Strategy and the Pricing of Debt Contracts

This article, which was originally written in 1986, develops a methodology for valuing mortgage-backed securities with refinancing costs. We solve simultaneously for the valuation of the mortgage-backed security (loan) and the borrower's refinancing strategy, pricing all coupon levels simultaneously. Because the borrower may refinance his or her loan and incur costs at many times in the future, the optimal refinancing decisions arise from an optimal dynamic strategy that reflects the costs of all potential future refinancings. Though the borrower faces multiple rounds of refinancing costs, the market value of the loan cannot exceed the call price plus a single round of refinancing costs.