The vast majority of America's farm laborers are immigrants, many of them undocumented. Farm work is notoriously dangerous, arduous and toxic; the average U.S. farmworker has a life expectancy of just 49 years. Farm laborers are generally paid piecework rates. Their average earnings are $7,500 a year, or $150 a week, by far the lowest wage of any occupation. Most farm laborers are denied overtime pay, medical insurance, sick leave or the right to organize. In many states they're excluded from workers' compensation and unemployment benefits. Of the more than 1 million farmworkers in this country, only about 27,000 are unionized.