With all the focus on America's southern border – on fences, National Guard troops, and detection – one might think the only source of illegal immigrants to the US is desert-crossers from Mexico. But that's only half the picture. Literally.
A study released last month by the Pew Hispanic Center estimates that people who overstayed their visas account for as much as 45 percent – nearly half – of the unauthorized immigrants now in the US. Most of the 4.5 million to 6 million people who violated their visas were tourist or business travelers. (The total also includes 250,000 to 500,000 who overstayed a visa known as a Border Crossing Card, used for frequent visitors.)
Pew regrets having to be inexact about the estimates, but the truth is, no one knows just how many people are overstaying visas, because the federal government can't accurately count them. That's right: Credit-card companies can alert customers the world over about fraudulent purchases, yet the feds can't keep track of how many people abuse visa privileges.
The government has tried to improve its count with an electronic entry-exit tracking program called US-VISIT, run by the Department of Homeland Security (DHS). Originally planned as an immigration-control tool so that officials will know if a visitor has left or not, it's taken on an antiterrorist function (two of the 9/11 hijackers were in the US on expired visas). US consular offices issuing visas abroad collect scanned photos and fingerprints and check them against a database of terrorists and criminals. At port of entry, these biometrics are used to verify the visa holder's identity.