Overstayers

". . . approximately 45 percent of the estimated 11 to 12 million people who are undocumented came on a valid visitor visa but overstayed. These visa “overstayers” come from every country in the world. For obvious geographic reasons, undocumented immigrants from countries other than Mexico, Canada, and Central America are more likely to have entered on a visitor visa and overstayed than to have crossed a border illegally.)

(Soerens and Hwang, p. 67)