Cato Institute, New Estimates of Effective Corporate Tax Rates on Business Investment:

This bulletin presents estimates of effective corporate tax rates on new capital investment for 83 countries. “Effective” tax rates take into account statutory rates plus tax-base items that affect taxes paid on new investment, such as depreciation deductions, inventory allowances, and interest deductions. Our calculations also account for other taxes that affect investment, such as retail sales taxes on capital purchases and asset-based taxes.

We find that the U.S. effective corporate tax rate on new investment was 34.6% in 2010, which was the highest rate in the OECD and the fifth-highest rate among 83 countries. The average OECD rate was 18.6%, and the average rate for 83 countries was 17.7%.