I'm enjoying this little game, so let's keep going.
How do you feel about the reliability of the GAO? It produced the report in 2005 that is most frequently cited.
Here were its findings relative to the numbers of aliens as a percentage of the prison population for 2001-2004 (page 15 of the report):
total * US citizens * aliens
2001: 154,290 * 111,866 * 42,424
2002: 161,110 * 117,037 * 44,073
2003: 170,365 * 124,302 * 46,063
2004: 178,512 * 129,804 * 48,708
That works out to 27.3% for 2004 and an average for the period of 27.3%. I would say that's pretty consistent.
Here's a link to the GAO report, titled Information on Criminal Aliens Incarcerated in Federal and State Prisons and Local Jails:
http://www.gao.gov/new.items/d05337r.pdf
Are we getting close to being able to agree that the percentage of aliens in our prisons is something over 25%?