Numerous studies have evaluated the impact of Extension on farm productivity and related outcomes. Here we use annual data from 1983 to 2010 covering the 50 U.S. states to examine the impact of Extension on net changes in the number of farmers. The historical transition of farmers out of U.S. agriculture raises the question of whether Cooperative Extension and underlying Hatch-funded research spending keeps farmers in agriculture or accelerates their exit. On balance, nearly 500,000 more farmers left than entered agriculture over the period studied. We estimate that without Extension, as many as 137,700 (or 28%) additional farmers would have disappeared on net. Overall, Extension programs are a remarkably cost effective way of keeping farmers in agriculture. Alternatively, shifting just 1.5% of federal farm program payments to Extension would have reduced net exits over this period by an estimated 11%, or 55,000 farmers.