Gwynn Guilford:

Mounting evidence suggests that the notion that the 2007 crash happened because people with shoddy credit borrowed to buy houses they couldn’t afford is just plain wrong. The latest comes in a new NBER working paper arguing that it was wealthy or middle-class house-flipping speculators who blew up the bubble to cataclysmic proportions, and then wrecked local housing markets when they defaulted en masse.
 Analyzing a huge dataset of anonymous credit scores from Equifax, a credit reporting bureau, the economists—Stefania Albanesi of the University of Pittsburgh, the University of Geneva’s Giacomo De Giorgi, and Jaromir Nosal of Boston College—found that the biggest growth of mortgage debt during the housing boom came from those with credit scores in the middle and top of the credit score distribution—and that these borrowers accounted for a disproportionate share of defaults.