From the Department of Homeland Security’s Office of Immigration Statistics:
During 2008, there were 175 million nonimmigrant admissions to the United States according to DHS workload estimates. These included tourists and business travelers from Canada, Mexican nationals with Border Crossing Cards, and all admissions requiring the submission of an I-94 form. I-94 admissions accounted for 23 percent (39 million) of the total admissions. The majority (90 percent) of I-94 admissions were short-term visitors, such as tourists and business travelers, while the remaining 10 percent (3.7 million) were temporary residents characterized by a longer duration of stay, such as specialty workers, students, and nurses. The leading countries of citizenship for I-94 admissions were Mexico, the United Kingdom, and Japan.
The report is online: “Nonimmigrant Admissions to the United States: 2008”
