ABSTRACT
This paper reviews studies that have attempted to measure the impact on
farmer knowledge, technology adoption, productivity and profits of public
sector investments in agricultural extension programs. Forty-seven studies
undertaken in 17 countries plus one international study covering 24 developing countries are reviewed. A number of these studies appeared to be subject to substantial bias because extension measures were endogenous to farmer behavior, i.e., extension contacts were chosen by farmers. Most studies measured positive impacts of extension. Those estimates least subject to bias, i.e., where extension variables were measured as services supplied to a region, were most consistent in showing impact. Only ten studies report estimated returns to investment in extension. These did report relatively high rates of return and demonstrated that agricultural extension in a number of countries has been a high pay-off public investment
