Empirical economic analysis is a powerful tool. It can elucidate correlations and sometimes even get us to causual explanations. But it has a serious weak-spot: its value is entirely dependent upon the integrity of the data analyzed. To put the problem succinctly: sh*t in, sh*t out.
This brings us to analyses of the housing bubble. There’s a sizeable academic literature on the housing bubble (and relatedly also expert witness reports on loss causation in MBS litigation) that rely on loan-level data. The problem is that a lot of that loan-level data is suspect. That should hardly be a surprise: the industry even referred to some products as “liar loans”. And there were also FBI Mortgage Fraud reports indicating an uptick in mortgage fraud. But it was easy for economists to ignore the data integrity problem as long as the problems were merely anecdotal (e.g., the mariachi musician with the six-figure income), and could be blissfully assumed to only affect a small number of loans.