Optimal Mortgage Design
研究了在收入波动且不可观测、止赎成本高、市场利率随机的情况下，最优抵押贷款的特征与可调整利率抵押贷款（option ARM）一致，借款人可自主决定还款额直至达到限额，违约率和利息支付与市场利率正相关，该合同对收入波动大、购房昂贵或首付低的借款人收益最大。
This article studies optimal mortgage design in a continuous-time setting with volatile and privately observable income, costly foreclosure, and a stochastic market interest rate. We show that the features of the optimal mortgage are consistent with an option adjustable-rate mortgage (option ARM). Under the optimal contract, the borrower is given discretion of how much to repay until his balance reaches a certain limit. The default rates and interest rate payment on the mortgage correlate positively with the market interest rate. Gains from using the optimal contract relative to simpler mortgages are the biggest for those who face more income variability, buy pricey houses given their income level, or make little or no down payment. Our model thus may help to explain a high concentration of option ARMs among riskier borrowers. The Author 2010. Published by Oxford University Press on behalf of The Society for Financial Studies. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org., Oxford University Press.