... illegal aliens.
CBO director Douglas Elmendorf offers a summary (cboblog.cbo.gov/?p=2248):
* In 2009, about 38 percent of foreign-born people in the United States were from Mexico or Central America; the next-largest group came from Asia and accounted for 27 percent of the total foreign-born population.
* About one-fifth of naturalized U.S. citizens were from Mexico or Central America; more than...
... Congressional Budget Office director Douglas Elmendorf testified to the Senate Finance Committee about various healthcare proposals, and his remarks are here ("Options for Expanding Health Insurance Coverage and Controlling Costs").
Evaluating the various claims is left for those more familiar with these issues, however one issue in our purview is this: