The 18.2 million Americans that were declared of having Mexican ancestry are not differentiated between those born to legal vs illegal immigrants , children brought illegally , those with stolen US Citizen 's SSNs and Identities and chain migration data .
While the national annual growth rate was still positive ( 1.0 % ) in the early years of the 2000s , the national net migration rate was negative ( -4.75/1000 inhabitants ) , given the former strong flow of immigrants to the United States ; an estimated 5.3 million illegal Mexican immigrants lived in the United States in 2004 and 18.2 million American citizens in the 2000 Census declared having Mexican ancestry .
Demographics of Mexico