Building a Credit Model Using GSE Loan-Level Data
This article outlines an approach for developing a loan-level model to predict the probability and timing of credit events that trigger investor losses in Fannie Mae and Freddie Mac’s recent Credit Risk Transfer (CRT) transactions.
The structure of the article is as follows. We begin with background on why the GSEs released loan-level data and how this disclosure is different from their previous data disclosures. We then compare the credit event, as defined in the GSEs’ CRT transactions, to other measures of credit performance and discuss the relevant population of data records to include in a development dataset. Next, we show how a simple model based only on limited set of loan characteristics can help explain variation in credit performance. And finally, we show how the inclusion of variables that capture the macroeconomic and credit-underwriting environment can improve the model fit over time and across different origination vintages.
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