What do we know about R&D spillovers and productivity? Meta-analysis evidence on heterogeneity and statistical power

As Mohnen (1996: 40) has indicated, research and development (R&D) externalities is a two-sided theoretical issue. Its ‘dark’ side concerns the under-investment problem caused by non-appropriability of R&D benefits. On the ‘bright’ side, R&D spillovers are a source of productivity gains. Both aspects have been invoked to justify public support for R&D investment directly and indirectly. To establish whether public support can be justified due to productivity gains from spillovers, we meta-analyse 983 productivity estimates for spillovers and 501 estimates for own-R&D from 60 empirical studies. Our findings indicate that the average spillover effect is: (i) positive but heterogenous and smaller than what is reported in most narrative reviews; (ii) usually smaller than that of own-R&D capital; (iii) too small to be practically significant when evidence with adequate statistical power is considered. Controlling for observable sources of heterogeneity and best-practice research, the meta-effect is insignificant in the full sample but significant and large among OECD firms/industries/countries. We discuss the implications of these findings for future research and public support for R&D investment.