Attribution and other problems in assessing the returns to agricultural R&D
研究了农业研发回报率估计中因时间、地点和机构不同导致的归因问题，指出过去研究高估回报率且变异大，并以美国小麦品种和计量模型中的研究滞后为例说明两类归因问题的重要性。
Abstract Estimated rates of return to research are distorted by problems of attributing the credit for particular research results, or for particular research‐induced productivity increases, among research expenditures undertaken at different times, in different places, and by different agencies. A comprehensive assessment of the evidence from past economic evaluations of the returns to agricultural R&D indicates that studies generally report high rates of return, with enormous variation among studies, but that much of this evidence has been tainted by inadequate attention to attribution problems. This paper raises these concerns in a general way and illustrates their importance with reference to two particular types of attribution problem. First, we consider the problem of accounting for locational spillovers in attributing varietal‐improvement technology among research performers, using US wheat varieties as an example. Second, we consider the temporal aspects of the attribution problem using the specification of research lags in econometric models to illustrate the problem of attributing aggregate productivity gains to research expenditures made at different times.