This chart as of 2005 is/was in Vitus' presentation on the crisis of 2008. It has been out on the net and referenced by many (eg) to show that Freddie and Fannie were loosing share to private ABS dealers during the run-up to the crisis and were thus NOT the proximate causes thereof. The updated chart below, via DeLong, is composed from data at the Census Beureau (item 1191 at link).
There are other things about the F/F meme that cry out to be on the short list of beliers. There is the fact that the GSE's were limited by charter to taking only loans with a maximum LTV of 80%. While they began about '06 to try to find ways around this, they did not have more than 10% of loans outstanding with greater than 80% LTV until April of '07. So, for F/F to have caused the crisis, they would have had to go from a standing start to world-destroyer in one year. Gimme break mon.
Also, if the CRA caused it all, why were there crises in most of the developed world - where the CRA did not apply. Many other references supplied on demand.