Using Markov Chains to Estimate Losses from a Portfolio of Mortgages.

Under Statement of Financial Accounting Standards Number Five, Accounting for Contingencies (SFAS 5), financial institutions record a provision for loan losses and establish loan loss reserves when impairment of a loan is probable and the loss can be reasonably estimated. Increasingly, Markov chain models are being used to estimate these losses. This paper develops and test the suitability and forecast accuracy of alternate Markov chain models of mortgage payment behavior using transition data from the Federal Home Loan Mortgage Corporation (Freddie Mac). In developing the models, the Freddie Mac transition data is examined to see if it satisfies the Markovian assumptions of stationary transition probabilities and homogenous payment behavior. The data examined in this paper did not satisfy these assumptions. With respect to accuracy in forecasting loan losses, the Markov chain approach, when incorporating recent information on transition probabilities, performed better than a random-walk model of loan losses. Copyright 1999 by Kluwer Academic Publishers