The purpose of CAPES is to estimate the market value of residential properties in order to assess the collateral on Countrywide mortgage loans. CAPES estimates market value by comparison of the subject property to other similar nearby properties, for which recent sales information is available. In some cases price indices describing the change in property values over time are also used. In addition to the estimated market value, CAPES produces a measure of the uncertainty in the result. It uses several models, including heuristics derived from companyspecific business rules, and accesses both commercial and proprietary property databases. Its accuracy has been validated extensively on batches of properties by comparing its results to known sales prices. It is integrated with Countrywide’s underwriting expert system and is currently being used by over thirty departments on a daily basis.