Now, Times That By 3

From the New York Daily News: The number of immigrants crossing into the U.S. illegally appears to be rising again after a big drop during the recession.
About 11.7 million undocumented immigrants were in the U.S. last year, up from 11.5 million in 2011, according to estimates released by Pew Research Center's Hispanic Trends Project on Monday.
The increase is within the researchers' margin of error, but Pew said the country's recession-era decrease in illegal immigration — including visa overstays and border crossings — has bottomed out. Illegal immigration peaked at 12.2 million in 2007 and dropped to 11.3 million in 2009, Pew researchers said.
"Whether this is an indication that the economy's improving enough to attract new unauthorized immigrants is hard to say," said Jeffrey Passel, Pew Research Center senior demographer.
Read more: http://www.nydailynews.com/news/national/illegal-immigration-levels-rising-u-s-study-article-1.1465076#ixzz2fnGn9eNk
With all due respect to Pew, that number is way, way off, it's probably more like 30+million illegals. 
Seriously, how do you document all the illegals?  Call and survey them via telephone?