R&D and Productivity: Estimating Endogenous Productivity
建立了一个内生生产率变化模型，研究知识投资对企业生产率的影响，使用西班牙制造业企业面板数据发现研发支出与生产率之间存在非线性和显著不确定性。
We develop a model of endogenous productivity change to examine the impact of the investment in knowledge on the productivity of firms. Our dynamic investment model extends the tradition of the knowledge capital model of Griliches (1979) that has remained a cornerstone of the productivity literature. Rather than constructing a stock of knowledge capital from a firm's observed R&D expenditures, we consider productivity to be unobservable to the econometrician. Our approach accounts for uncertainty, non-linearity, and heterogeneity across firms in the link between R&D and productivity. We also derive a novel estimator for production functions in this setting. Using an unbalanced panel of more than 1800 Spanish manufacturing firms in nine industries during the 1990s, we provide evidence of non-linearities as well as economically significant uncertainties in the R&D process. R&D expenditures play a key role in determining the differences in productivity across firms and the evolution of firm-level productivity over time. Copyright 2013, Oxford University Press.