Roughly 3.2 million persons work on farms, most part time One million of them are hired workers (i.e. not members of an operating family). They are largely full time and account for 60% of labor hours on farms. Most are foreign-born, and many of them are undocumented. Perhaps 150,000 undocumented persons work full time on California farms. (Go here and here.) This is by far the greatest concentration of undocumented workers, within one industry and one state. They are about 8% of the undocumented workforce in California and 1% of the state’s entire workforce.
(The undocumented workforces in construction labor and housekeeping are larger but they are scattered throughout the country.)
What would happen if these California workers, who earn about $10 an hour, gained legal status? Philip Martin on the University of California /Davis considers the impact on wages. It’s likely that (1) they will demand higher wages and (2) consider better jobs off the farm, thus reducing the farm labor pool. (Go here and here.)
When the Bracero program ended in 1962, the United Farm Workers union won a 40% wage increase for some table grape workers. Assuming that these newly enfranchised workers win a similar wage increase, Martin estimates that the price of a pound of apples would increase by 4%. Per Martin, 40% increase in farm labor costs translates into a 3.6% increase in retail prices, costing households not much but raising the annual income of the workers from $10,000 to $14,000.