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Short and Long-Run Returns to Agricultural R&D in South Africa, Or Will the Real Rate of Return Please Stand Up?

David SchimmelpfennigColin ThirtleJohan van ZylCarlos ArnadeYougesh Khatri

出版	SSRN, 2015
URL	http://books.google.com.hk/books?id=kwvczwEACAAJ&hl=&source=gbs_api

註釋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.