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标题：Short and long-run returns to agricultural R&D in South Africa, or will the real rate of return please stand up?
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作者：Schimmelpfennig, David ; Thirtle, Colin ; Zyl, Johan van 等
期刊名称：Journal of Agribusiness
印刷版ISSN：0738-8950
出版年度：2000
页码：1-15
出版社：Journal of Agribusiness
摘要：This paper briefly presents the results of a total factor productivity (TFP) study of South African commercial agriculture, for 1947-1997, and illustrates some potential pitfalls in rate of return to research (ROR) calculations. The lag between R&D and TFP is analyzed and found to be only 9 years, with a pronounced negative skew, reflecting the adaptive focus of the South African system. The two-stage approach gives a massive ROR of 170%. The predetermined lag parameters are then used in modeling the knowledge stock, to refine the estimates of the ROR from short- and long-run dual profit functions. In the short run, with the capital inputs treated as fixed, the ROR is a more reasonable 44%. In the long run, with adjustment of the capital stocks, it rises to 113%, which would reflect the fact that new technology is embodied in the capital items. However, the long-run model raises a new problem since capital stock adjustment takes 11 years, 2 years longer than the lag between R&D and TFP. If this is assumed to be the correct lag, the ROR falls to 58%, a best estimate. The paper draws attention to the possible sensitivity of rate of return calculations to assumed lag structure, particularly when the lag between changes in R&D and TFP is skewed. © 2000 Elsevier Science B. V. All rights reserved.
关键词：South Africa;TFP;Returns to agricultural R&D;Profit function