One method of estimating this population is called the âresidual methodologyâ where the reported census number of self proclaimed foreign born people in the U.S. census is subtracted from the known number of legal immigrants to obtain the illegal alien (residual) population[5]. This methodology is used by the US Department of Homeland Security, Pew Hispanic Center, the Census Bureau and others. Since illegal aliens have many reasons for not answering the census correctly and no penalties for answering the census incorrectly a direct subtraction has a well known source of under count error and has to be corrected. All known users of this methodology correct the foreign born population (~ 35-50 million) by 10-40% (3-12 million) to account for this under count effect. Critics claim this correction is in error--whatever size correction is used.
Using the residual methodology with a minimal 10% foreign born undercount correction (reason for correction size unstated) for the 2000 Census and a 700,000 net illegal alien increase/year assumption and data from the March 2004 Current Population Survey [CPS Survey] (U.S. Census Bureau and Department of Labor) Pew came up with 10.3 million illegal aliens in 2004. Assuming the same rate of growth Pew estimates this population reached at least 11 million as of March 2005 [6].
The Pew Hispanic Center (Estimating the Size and Characteristics of the Undocumented Population; Figure 3) estimates that in the 1980âs net illegal immigration was at the 130,000 per year increasing to 450,000 /year from 1990-94, and further increasing to 750,000 /year from 1995-1999 and staying at 700-850,000+ /year since about 2000. Illegal Mexican immigration amounts to about 500,000 /year of this influx since about 1999. According to the same Pew Hispanic Center study as of March 2005, the illegal alien population had reached 11 million or more including more than 6.5 million illegal Mexicans (~60% of all illegals). Assuming the same rate of growth as in recent years gives about 12,000,000 illegal aliens in the United States as of January 2006, increasing at 700-850,000 per year with illegal Mexicans amounting to about 60%+ (~7+ million) of the total by 2006 and an ever increasing percentage as time progresses. By September 2006 the illegal population is thought to be about 13 million. About one-sixth of the illegal alien population--about 2.0 million people--is under 18 years of age.
