Do tax incentives for research increase firm innovation? An RD Design for RD

We present the first evidence showing causal impact of research and development (R&D) tax incentives on innovation outcomes. We exploit a change in the asset-based size thresholds for eligibility for R&D tax subsidies and implement a Regression Discontinuity Design using administrative tax data on the population of UK firms. There are statistically and economically significant effects of the tax change on both R&D and patenting, with no evidence of a decline in the quality of innovation. R&D tax price elasticities are large at about 2.6, probably because the treated group is from a sub-population subject to financial constraints. There does not appear to be pre-policy manipulation of assets around the thresholds that could undermine our design, but firms do adjust assets to take advantage of the subsidy post-policy. We estimate that over 2006-11 business R&D would be around 10% lower in the absence of the tax relief scheme.