The main impact of subprime lending on the overall mortgage business was the take-out function. As subprime lending grew, you saw better “performance” of prime or near-prime mortgage portfolios. This was not because subprime lending did away with the traditional default drivers of job loss, illness, divorce, or disorderly conduct; it was because loans in that kind of trouble had a place to go besides foreclosure. Prime lenders could and did congratulate themselves on their low foreclosure rates as if it were a matter of their superior underwriting skills, but that involves a high degree of naiveté. It’s really important to understand this issue, because it gets to the heart of the “contagion” thing. It is not that subprime delinquencies are “spreading” to prime loans as if some infectious agent were in play. It’s that the drain got backed up: when subprime lenders go out of business, or investors won’t buy subprime loans, there is no place for the inevitable prime delinquencies to go except foreclosure. Prime delinquencies become “visible” because they don’t move out of the prime portfolio via refinance into the subprime portfolio, where we “expect” to see them.