ECNOMIC CONTRIBUTION

Agricultural extension programmes are quite diverse from an international perspective. Most are managed as public sector agencies, usually located in the ministry of agriculture, but some are located in other ministries such as education or rural development. Many are managed by nongovernmental organizations (NGOs). Many private firms and private organizations (for example, coffee-growers' associations) conduct extension programmes. Even within the most typical organizational structure, where extension is part of the government's ministry of agriculture, there is great variation in the degree of decentralization of management of extension services. In some countries, extension is decentralized, as in India, where it is a state subject. In most developing countries, however, governmental services are highly centralized, with varying forms of regional and subregional units designed to serve local areas.

Further, there is great variation in the skill level and agricultural competence of field staff. In some systems, field staff have little formal technical training in the agricultural sciences. In some cases, this is dictated by a village worker philosophy, in others by local language demands. But, in most cases, it simply is the result of the decisions to expand agricultural extension programmes rapidly during the 1950s and 1960s, when few highly trained agriculturalists were available (see Bindlish & Evenson, 1993 and Bindlish, Gbetibouo, & Evenson, 1993 for African studies; and Swanson & Claar, 1984 for a general history).

Finally, this diversity of skills, management systems, and objectives has changed over time in many countries. Perhaps the major changes in the management and design of agricultural extension systems over the past four decades is associated with the training and visit (T&V) system introduced in the 1970s by Benor, Harrison, and Baxter (1984) and implemented in many countries with World Bank lending support.

Given this diversity, broad generalizations about the economic contribution of agricultural extension to agricultural development are not feasible. Many situation-specific factors impinge on the effectiveness of extension programmes. The fact that substantial reform and redesign of many extension programmes has taken place indicates that some of them were perceived by their supporters to have been less than fully effective. However, we now have a substantial body of economic studies of extension services in a number of countries; 75 studies of economic impacts of extension systems have been published to date. My task in this chapter is to review the findings of 57 of these studies and to draw out some of the lessons they have to offer.

I begin this review with a brief summary of investment patterns for both agricultural research and extension. This is designed to provide historical perspective and to call attention to some of the economic and institutional diversity in which extension systems must function. In the second section, I review the conceptual foundation for measuring the economic impact. Statistical procedures are reviewed in the third section, and in the fourth I summarize the findings of the studies under review and attempt to relate these to some of the differences in economic and institutional settings. In the final part, I summarize policy lessons