This chart is a screen capture of the original which appeared on the Mark Thoma's blog The Economist's View. See the original chart and post accompanying it.
Thoma has waaaay more understanding of this than I do. He's got the nifty cool graphs and charts to back up what I tried to say on October 4.
Namely, Fannie and Freddie did not cause the foreclosure crisis. As the chart shows, The Two F's got out of subprime loans in 2002 before things got really crazy. Watch the pink line - see how it dips sharply at the sime time the dotted light blue line makes a jump shot? That's Fannie and Freddie getting the heck out of dodge, because the loans the market started demanding felt way too risky. The light blue line is "asset-backed securities issuers," namely entitities like the investment banks that have failed so spectacularly of late.
The Two F's were still giving out some loans more risky than their standard fare. But as Thoma explains (and my personal experience proves) Fannie and Freddie largely did 30-year fixed rate loans. They weren't doing the "exotic" liar loans that have caused so much pain.
Thoma says, "There is no excuse for the actions of the management of Fannie and Freddie, and I'm not trying to defend them or their choices, but the idea that Fannie and Freddie caused the general credit crisis is wrong." (emphasis mine).
By the way, I'm still browsing through Thoma's blog, trying to study up on all the intricacies he and his colleagues discuss about economics in general and the housing/financial crisis in particular. It's not for bare beginners, but is an excellent resource if you've done some reading on the basics elsewhere. Check it out!