The "12 million undocumented and illegal immigrants" residing in our country have fueled the national discourse on immigration reform. The number is repeatedly cited by immigration reform advocates like CNN's Lou Dobbs looking to incite support for their policies in curtailing the influx of foreigners. But few politicos and pundits ever stop to ask two questions fundamental to the immigration debate: How do we calculate the number of illegal immigrants? And where did the number 12 million come from?
The methodology for counting unauthorized immigrants relies on a lot of assumptions which call into question the accuracy of the results. Twelve million may be the most popular number cited for illegal immigrants in the U.S at present, but some estimates, like one from Bear Stearns, believe the count is actually closer to a whopping 20 million.
The different estimates stem from the varied methodologies used to arrive at a figure. Most approximations of the size and characteristics of the illegal immigrant population use the "residual method," pioneered by Jeffrey Passel of the Pew Hispanic Center. It is Dr. Passel who first came up with the estimate of 12 million illegal immigrants. The most recent estimate by the Department of Homeland Security (DHS) on the unauthorized population also uses the residual method.
The residual method uses a 2000 U.S. Census survey as its starting point because it yields an estimate on the number of foreign-born residents. Researchers subtract the number of immigrants who were authorized to come to the U.S. from the number of foreign-born residents counted by the Census Bureau. This number is then adjusted using estimates of immigrant deaths and migration, and to account for Census undercounting.
Because the estimate of foreign-born individuals living in the U.S. derived by the Census relies on survey respondents to answer the Census questionnaire honestly, and because the survey was done eight years ago, neither the estimate of foreign-born individuals nor the 12 million illegal immigrant estimate can be trusted. Are we to believe that houses full of illegal immigrants would give an accurate count of the people inside their home to Census takers? Even more absurd is the belief they would even fill out the survey or be found by the Census in the first place.
DHS anticipates the undercounting and adjusts their illegal immigrant estimates by a rate of 10% to account for it. But the adjustments amount to nothing more than guesswork; they are made without any means of precision.
‘Outmigration' also throws off estimates of illegal immigrants. Outmigration occurs when authorized immigrants leave the country or die. The events-which are projected from norms rather than recorded-alter the accuracy on the legal resident immigrant count used to calculate the number of illegal immigrants. Even Dr. Passel confesses that Outmigration is "hard to measure."
In 2005, Bear Stearns analysts determined that the surveys conducted by the Census Bureau undercounted the number of illegal immigrants by far more than 10%. Through discussions with illegal immigrants, Bear Stearns found that immigrants avoid responding to Census questionnaires and work very hard to conceal their identities.
As an alternative to the residual method, Bear Stearns used micro-economic indicators to project an alternative estimate. They examined trends in school enrollment, foreign remittances and housing permits in states with high populations of undocumented immigrants like Texas, California, and New York.
Underpinning Bear Stearns' estimate of 20 million illegal immigrants is the identification of two patterns: 1) a trend of sharply increased demand for public services in communities that have become gateways for immigration, and 2) increases in foreign remittances (money sent back to an immigrant's native country), housing permits and border-crossings.
Given the unrecorded nature of the illegal immigration phenomenon, it's unlikely that a well-founded or rigorous method of measurement will be developed. The reality is, the math is fuzzy and the most definitive conclusion one can make is that the measurements of illegal immigrants in the U.S. are subject to extreme inaccuracies.
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