In January 2009, when President Barack Obama first took office, says the BLS, there were 21,375,000 foreign-born people employed in the United States. In August 2013, there were 23,833,000 foreign-born workers employed in the United States. That means that since Obama took office the number of foreign-born people holding jobs inside the United States has increased by 2,458,000.
By contrast, in January 2009, there were 119,061,000 native-born Americans employed in the United States, and, in August 2013, there were 120,676,000—an increase of 1,615,000.
The 2,458,000 increase in foreign-born workers since January 2009 is 843,000 (or 52 percent) greater than 1,615,000 increase in native-born workers.
The BLS numbers are based on a survey of 60,000 households that the Census Bureau conducts each month. That survey does not distinguish between foreign-born persons who are naturalized U.S. citizens, legal permanent U.S. residents, work-visa holders or “undocumented” foreign nationals working illegally in the United States. Rather, it counts them all simply as foreign-born individuals who are in the United States and who are either working or not working. The survey focuses on persons who are 16 years old or older.
The BLS numbers also show that the labor-force participation rate for both the foreign-born and native-born population has declined under Obama, although the native-born participation rate has dropped more than the foreign-born participation rate.
In January 2009, when Obama took office, the labor-force participation rate among foreign-born persons 16 years or older was 67.2 percent. By this August, it was down 66.9 percent. In January 2009, 65.0 percent of native-born Americans 16 years or older participated in the labor force. By August, that was down to 62.8 percent.
BLS counts someone as participating in the labor force if they are 16 or older and either have a job or have actively sought one in the last four weeks.
Source material can be found at this site.