USAToday reported February 25 that “Half the problem is people who enter legally, then stay illegally.” The article asserts that “As many as 45% of the nation’s illegal immigrants — perhaps 5 million people — entered the U.S. legally but failed to leave.” The article sources that statistic to a 2006 report of the Pew Hispanic Center. Pew’s estimate was based on a Census Bureau survey.

It is obviously tricky to base estimates about illegal aliens on a government survey, because illegal aliens do not willingly provide information to government agents. But, besides that, there is good reason to question that the share of illegal aliens could be as large as 45 or 50 percent.

Survey work done after the 1986 amnesty asked aliens who gained legal status how they entered the country. These people had legal status so they had no reason to hide from the interviewers. The result was that 21 percent of them said they entered with visas. But that number is deceptive because the survey was done only among the illegal aliens who got amnesty as a result of living in the United States since before the amnesty eligibility date in 1982. Another two-fifths of the amnesty recipients applied under a separate provision for agricultural workers. It is unlikely very many of them entered with visas. If those additional amnesty recipients were added into the other amnesty sample, the rate of visa overstayers would drop to less than 13 percent.

The illegal alien population is much larger today – nearly 12 million – than it was in 1986, and the number of illegal workers in agriculture has remained about the same. It is hard to imagine that the share of visa overstayers has increased from about 13 percent to 45 to 50 percent.

Why would anyone care what share of the illegal aliens are visa overstayers? Visa overstayers are generally much more educated and prepared to take well-paying jobs than those who sneak into the country. The higher the visa overstayer share, the more it bolsters arguments that a new amnesty will not place a major burden on the U.S. taxpayer for the social services that the amnestied population will become eligible for.