In 1986 when the study began, agriculture was one of the largest employers in the United States, comprising nearly 12 million people. Farm workers were hospitalized more frequently than other occupational groups and were found to have the highest number of restricted activity days due to injury and illness. Much of this was due to frequent and disabling farm related accidents which made agriculture the most hazardous occupation in the United States. Agricultural workers were also found to have high rates of respiratory disability, compared with other industrial sectors, based on Social Security disability records.