Theories of rational redlining suggest thinness in housing markets should lead to greater uncertainty in house price appraisals, increasing mortgage denial rates or pricing. Empirical tests found support for this theory in mortgage underwriting using 1990s data. Using 2006 data and bank-specific regression models, we revisit this topic in light of two developments leading to the recent mortgage bubble: the widespread securitization that allowed banks to shift loan risk to investors and the advent of risk-based pricing. Consistent with expectations, we find that information externalities have become economically very small and have shifted from underwriting to pricing decisions.Theories of rational redlining suggest that the number of recent house sales in a given neighborhood represents an "information externality," with the implication that a low volume of sales should lead to greater uncertainty about appraised house values, making the mortgage loan less attractive to lenders and consequently more likely to be denied or charged a higher price. Previous empirical tests of this theory are limited solely to the implications with respect to the underwriting (accept/reject) decision. Additionally, those tests are based on data that preceded the recent mortgage bubble. The period of the mortgage bubble, however, offers a unique time frame for studying information externalities in lending. First, easy securitization enabled banks to sell many of the loans they underwrote, making them unaccountable for the riskiness of their loans. 1 We therefore test whether the effect of information externalities on denial decisions decreased during the mortgage bubble. Second, in the early 2000s, lenders extended mortgage underwriting to applicant segments previously deemed too risky, with pricing being the mechanism by which investors were compensated for the increased risk. We therefore test whether the effect of information externalities has shifted from underwriting to pricing, this being the first study of the pricing implications of the information externality theory.We further contribute to the existing literature by testing whether information effects play a lesser role in home purchase lending than in refinancing. Underlying this hypothesis is the fact that appraisal accuracy may be less important in home purchase lending, where the property sale price is known.Testing the information externality theory has important public policy implications. First, if information externality theory is true, government intervention is justified even in the absence of "traditional" discriminatory redlining. Second, it has fair lending implications: if low sale volume areas tend to have higher concentrations of minorities, omission of information variables may lead to the misidentification of lending patterns resulting from economically rational decisions by lenders as the presence of irrational redlining.The empirical analysis in this article uses extremely rich data and employs wellspecified, bank-specific regression models that explain ...