I think there is at least one additional and important piece of data in support of your argument which, to my mind, has been underplayed in this whole discussion. FHFA released a research report in Sept. 2010 entitled "Data on the Risk Characteristics and Performance of Single-Family Mortgages Originated in 2001 - 2008 and Financed in the Secondary Market." Of particular importance is Figure 8 (page 16), entitled "Ever 90-Day Delinquency Rates on Higher Risk Single-Family Mortgages Originated from 2001 through 2008 and Sold into the Secondary Market, by Origination Year." While not a great title, the graph shows that for Higher Risk loans, PLS default rates were ALWAYS higher than GSE loans for vintage 2001-2007 loans. A frequently repeated claim is that the GSEs (whether or not through their "affordable" goals) caused a reduction in underwriting standards and therefore caused the crisis. As you point out, this is false - despite some bad actions by the GSEs. What this Figure 8 demonstrates is that it PLS defaults for similarly situated borrowers were substantially higher. Private securitization cannot be blamed entirely for the crisis: but it cannot be excused. These data seems to suggest that PLS underwriting was worse than the GSEs. The report and data can be found at: http://www.fhfa.gov/Default.aspx?Page=313 (but I can't seem to link to the Figure itself).