This annual report from the U.S. Department of State contains information on waiting times for family-based and employment-based immigrant visas as of November 2012. The report shows nearly 4.3 million applicants waiting for family-based immigrant visas, and another 113,000 applicants waiting for employment-based visas. Over 1.3 million of those waiting applicants are from Mexico, almost all in the family-based immigrant categories. The countries where the most applicants for employment-based immigrant visas are waiting are the Philippines, India, China, South Korea, and Mexico.
These waiting times and backlogs are actually longer because these lists are based solely on pending applications at U.S. embassies and consulates outside the U.S. and do not account for applications for adjustment of status filed by applicants living in the U.S. These additional adjustment of status applications are added to the waiting lists and will further delay many of the waiting times listed in the report.