Aggregate implications of innovation policy

"We present a tractable model of innovating firms and the aggregate economy that we use to assess the link between the responses of firms to changes in innovation policy and the impact of those policy changes on aggregate output and welfare. We argue that the key theoretical determinant of the relative long-run aggregate impact of alternative policies is their impact on the expected profitability of entering firms. We show that, to a first-order approximation, a wide range of policy changes have a long-run aggregate impact in direct proportion to the fiscal expenditures on those policies, and that to evaluate the aggregate impact of such policy changes, there is no need to calculate changes in firms' decisions in response to these policy changes. We use these results to compare the relative magnitudes of the impact on aggregates in the long run of three innovation policies in the United States: the Research and Experimentation Tax Credit, federal expenditure on R&D, and the corporate profits tax. We argue that the corporate profits tax is a relatively important policy through its negative effects on innovation and physical capital accumulation that may well undo the benefits of fed