This paper studies how to incorporate observable factors in difference-in-differences and document their empirical relevance. We show that even under random assignment directly adding factors with unit-specific loadings into the difference-in-differences estimation results in biased estimates....

Using household survey data, we document evidence of a loosening of credit standards in Euro area countries that experienced a property price boom-and-bust cycle. Borrowers in these countries exhibited significantly higher loan-to-value (LTV) and loan-to-income (LTI) ratios in the run up to the...