Mark, Andy: Take a look at this link.
There are two documents there–taking the count of unauthorized immigrants both in 2000 and in 2005. The 2000 number is around 7 million; the 2007 number (an extrapolation of 2005) is around 12 million. So way more than 25% of the illegals entered under Bush–even if we use the “official” counts published in the DHS website.