When we break out the volume of mortgage origination from 2002 to 2006 by income deciles across the US population, we see that the distribution of mortgage debt is concentrated in middle and high income borrowers, not the poor. Middle and high income borrowers also contributed most significantly to the increase in defaults after 2007.
There is also this:
Poorer areas saw an expansion of credit mostly through the extensive margin, i.e. a larger numbers of mortgages originated, but at DTI levels in line with borrower income.
That is from the new NBER working paper by Adelino, Schoar, and Severino. In other words, poor people (or various ethnic groups, in some accounts) were not primarily at fault for the wave of mortgage defaults precipitating the financial crisis. The biggest problems came in zip codes where home prices were having large run-ups. Their conclusion is:
These results are consistent with an interpretation where house price expectations led lenders and buyers to buy into an unfolding bubble based on inflated asset values, rather than a change in the lending technology.
Changes in policy, of course, also for this context would count as “a change in the lending technology.”