Corporate Income Taxes , Financial Constraints and Innovation ∗

We examine exogenous changes in state corporate income taxes over the 1988-2006 period and find that tax decreases significantly boost both the quantity, measured by the number of patents, and the quality, measured by citations per patent, of innovative output, while tax increases have little impact on innovation. Most of the impact of tax changes on innovation occurs two or more years after the tax change, which alleviates concerns of reverse causality. Further tests examine the channels through which tax decreases affect innovation. We document that tax decreases have stronger impact on innovation for more financially constrained firms, for firms with weaker governance and for firms that engage in tax avoidance to a greater extent. The latter result suggests that, after a tax decrease, firms can allocate more resources to innovative activities rather than to tax avoidance. We conduct numerous additional tests to demonstrate that our results are not spurious and not subject to endogeneity biases. JEL Classification: G31, G32, G34, G38