Undocumented immigrant population of the United States

[14] Critics claim that the estimate is unreliable for a number of reasons: figures for outmigration are not tracked by the federal government; the proportion of undocumented immigrants who respond to the Census is unknown; the estimate that 10% of undocumented immigrants do not respond to the census is arbitrary and unsupported by a sufficient sample size and geographic spread; and that the self-reporting of where one was born relies on the honesty of the person being questioned.

[16][11] A 2018 paper by three Yale School of Management professors yielded similar trajectories of the undocumented immigrant population, with peak growth in the 1990s and early 2000s followed by a plateau from approximately 2008 onward.

That result, however, was criticized for vastly overstating the true number and for failing to account for the circular flow rate.

The construction sector and other areas where undocumented immigrants traditionally seek employment shrank.

The recession also led to a surplus of American labor, driving down the benefit of hiring undocumented immigrants.

[18] After the Great Recession, more immigrants actually returned to Mexico rather than migrated to the United States.

[20] The number of Mexican legal and undocumented immigrants in the United States grew quite rapidly over the 35 years between 1970 and 2004; increasing almost 15-fold from about 760,000 in the 1970 Census to more than 11 million in 2004—an average annual growth rate of more than 8 percent, maintained over more than three decades.

[citation needed] On average the net Mexican population, both documented and undocumented, living in the United States has grown by about 500,000 per year from 1995 to 2005 with 80 to 85 percent of the growth attributed to unauthorized immigration.