Have R&D spillovers changed?
This paper revisits the results of Bloom, Schankerman, and Van Reenen (2013) examining the impact of R&D on the performance of US firms, especially through spillovers. We extend their analysis to include an additional 15 years of data through 2015, and update the measures of firms' interactions in technology space and product market space. We show that the magnitude of R&D spillovers appears to have been broadly similar in the second decade of the 21st Century as it was in the mid-1980s. However, there does seem to have been some increase in the wedge between marginal social returns to R&D and marginal private returns with the ratio of marginal social to private returns increasing to a factor of 4 from 3. There is certainly no evidence that the divergence between public and private return has narrowed. Positive spillovers appeared to increase in the 1995-2004 boom.