Do they have any evidence that the default rate on 401(k) loans might have doubled after 2008? No. Well, they have a tiny bit of evidence: they look at the small variations in default rates in each of the three years covered in the Wharton study, and see that those variations move roughly in line with the national unemployment rate. Never mind that the default rate fell, from 9.9% to 9.7%, between 2006 and 2008, even as the unemployment rate rose, from 4.8% to 5.0%. They've still somehow managed to convince themselves that it's reasonable to assume that the default rate today is nowhere near the 9.6% seen in the Wharton survey, and in fact is probably closer to - get this - 17.9%.