Recent trends in coverage of the Mexican-born population of the United States: results from applying multiple methods across time.

The accuracy of counts of U.S. racial/ethnic and immigrant groups depends on the coverage of the foreign-born in official data. Because Mexicans constitute by far the largest single national-origin group among the foreign-born in the United States, we compile new evidence about the coverage of the Mexican-born population in the 2000 census and 2001-2010 American Community Survey (ACS) using three techniques: a death registration, a birth registration, and a net migration method. For the late 1990s and first half of the 2000-2010 decade, results indicate that coverage error was somewhat higher than currently assumed but had substantially declined by the latter half of the 2000-2010 decade. Additionally, we find evidence that U.S. census and ACS data miss substantial numbers of children of Mexican immigrants, as well as people who are most likely to be unauthorized: namely, working-aged Mexican immigrants (ages 15-64), especially males. The findings highlight the heterogeneity of the Mexican foreign-born population and the ways in which migration dynamics may affect population coverage.