One number jumps out when comparing the new immigration reform bill and the 2007 legislative effort: 16.2 million.

That's how much the U.S. population would grow as a result of the Gang of Eight bill in the first 20 years after passage, according to the Congressional Budget Office.

By comparison, CBO projected no increase in population 20 years after the 2007 bill, with tougher enforcement fully offsetting the relatively modest increases in the legal immigrant population.