摘要: Anderson and Feder analyze the considerations that lead policymakers to undertake extension investments as a key public responsibility, well complex set of factors intra-agency incentives explain why different systems' performance vary. The authors provide conceptual framework outlining farmers' demand for information, welfare economic characterizations services, organizational political attributes govern systems. They use examine several modalities their likely actual effectiveness. Specifically, reviewed include "training visit" extension, decentralized systems, "fee-for-service" privatized farmer-field-schools. also discuss methodological issues pertaining assessment outcomes review empirical literature on impact. emphasize efficiency gains can come from locally delivery systems with incentive structures based largely private provision in most poorer countries is still publicly-funded. In wealthier countries, particular higher income farmer groups, will evolve into fee-for-service organizations. This paper - joint product Agriculture Rural Development Department Development, Research Group part larger effort Bank study opportunities challenges facing agricultural extension.