Up or Down? Capital Income Taxation in the United States and the United Kingdom

Empirical evidence suggests that the Effective Marginal Tax Rate (EMTR) on income from capital has increased considerably in both the United States and the United Kingdom during 1982–2005. The corporate tax literature predicts however that the EMTR should fall over time due to increasing international capital mobility and higher tax competition between governments. This paper argues that this inconsistency can be explained by the fact that EMTRs are currently computed from versions of the neoclassical investment model that omit deferred tax constraints faced by firms investing in both the United States and the United Kingdom.