A reinvestment in agricultural R&D is critical to ensuring sufficient food for the world in the coming decades.

A total of 289 studies of returns to agricultural R&D were compiled and these provide 1821 estimates of rates of return. After removing statistical outliers and incomplete observations, across the remaining 1128 observations the estimated annual rates of return averaged 65 per cent overall ö 80 per cent for research only, 80 per cent for extension only, and 47 per cent for research and extension combined. These averages reveal little meaningful information from a large body of literature, which provides rate-of-return estimates that are often not directly comparable. This study was aimed at trying to account for the di¡erences. Several features of the methods used by research evaluators matter, in particular assumptions about lag lengths and the nature of the research-induced supply shift.

The past 50–100 years have witnessed dramatic changes in agricultural production and productivity, driven to a great extent by public and private investments in agricultural research, with profound implications especially for the world's poor. In this article, we first discuss how the high-income countries like the United States represent a declining share of global agricultural output while middle-income countries like China, India, Brazil, and Indonesia represent a rising share. We then look at the differing patterns of agricultural inputs across countries and the divergent productivity paths taken by their agricultural sectors. Next we examine productivity more closely and the evidence that the global rate of agricultural productivity growth is declining—with potentially serious prospects for the price and availability of food for the poorest people in the world. Finally we consider patterns of agricultural research and development efforts.

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