Nber Working Paper Series Is Public R&d a Complement or Substitute for Private R&d? a Review of the Econometric Evidence

Is public R&D spending complementary and thus “additional” to private R&D spending, or does it substitute for and tend to “crowd out” private R&D? Conflicting answers are given to this question. We survey the body of available econometric evidence accumulated over the past 35 years. A framework for analysis of the problem is developed to help organize and summarize the findings of econometric studies based on time series and cross-section data from various levels of aggregation (laboratory, firm, industry, country). The findings overall are ambivalent and the existing literature as a whole is subject to the criticism that the nature of the “experiment(s)” that the investigators envisage is not adequately specified. We conclude by offering suggestions for improving future empirical research