Yesterday the Census Bureau released its first set of data on the size of the foreign-born population in 2010.

The estimate based on the American Community Survey (ACS) – which supplements data collected in the Census – is that there were nearly 40 million immigrants – 13 percent of the population. The ACS data for 2010 takes into consideration the results of the 2010 Census and adjusts its estimates accordingly. So, it is noteworthy that the estimate of the foreign-born population jumped from the 2009 ACS estimate by nearly 1.5 million persons. That compares with an annual average increase in the ACS estimated foreign-born population between 2000 and 2009 of slightly more than 800,000.

The implication here is that the ACS sampling was significantly underestimating the amount of the foreign-born population increase. This is not surprising. A similar finding occurred after the 2000 Census, at which time, the Census Bureau conceded that the discrepancy likely resulted from an underestimate of the illegal alien population by the annual survey used to make estimates at that time.