AGRICULTURAL RESEARCH EXPENDITURES AND AGRICULTURAL PRODUCTIVITY CHANGE
质疑了在分析农业研究支出与生产率关系时常用的Almon滞后约束（尤其是端点约束）的有效性，指出这些约束可能导致有偏估计，并怀疑现有数据能否建立有意义的关系。
This note comments on the econometric analysis of the dynamic relationship between agricultural research expenditures and agricultural productivity change. The validity of the Almon restrictions, particularly endpoint restrictions, commonly imposed on the distributed lag is questioned. It is suggested that models incorporating such restrictions may lead to biased estimates of the effects of research spending. More fundamentally, doubts are raised as to whether any meaningful relationship between research spending and productivity change can be established from the available data.