The unauthorized share of US crop workers rose from 12 percent in 1989-90, just after IRCA legalization, to over half by 1997-98, but has since stabilized. Authorized workers earn about 10 percent more than unauthorized workers, in part because they have an average 12 years of US farm work experience, compared to four for the unauthorized. http://www.dol.gov/asp/programs/agworker/report9/toc.htm)