The study examined the effect on the cost of extending unemployment insurance protection to agricultural workers if interstate workers reduced their migration for employment as a result of such a program. There were 50,425 migrants in 14 states who had agricultural employment earnings in more than one state during a 52-week period. Two sets of adjustments were made on workers eligible for unemployment insurance benefits on the basis of agricultural coverage if they were not already eligible by previously covered nonfarm employment: 50% reduction and 100% reduction in interstate weeks of employment. Workers whose employment histories were adjusted had as nearly as possible 50% and 100%, alternately, of their interstate employment deleted to stimulate the phenomenon under study. If deleted, a job was deleted in its entirety. Similarly, no job was deleted which made a worker ineligible for benefits. The effective reductions in interstate employment when taken over all migrant workers were 20% and 71% for the two reductions, respectively. With no changes in migratory work histories, the extension of unemployment insurance coverage to employers with one or more workers in 20 or more weeks or a high quarterly payroll of $1,500 or more resulted in a cost rate of 4.78 for migrants separately and 2.95 for all agricultural workers taken together. This rate taken over all workers increased to 3.79 after the 50% reduction and to 6.15 after the 100% reduction. Average earnings plus benefits for migrants were $3,534. (Author/NQ)