Despite a growing interest in the rise in top incomes, there is still substantial disagreement about the causes and their relative importance. Studies suggest that in a country with a top marginal tax rate of 50%, a cut in the marginal tax rate by 1% would boost taxable income by 1%. For example, capital gains are often taxed at a lower rate than other income and, in a few countries, they are not taxed at all. Stock options also benefit from preferential tax treatment in many OECD countries (OECD, 2006a) and the same is likely to hold for carried interest arrangements. Why are top earners getting a growing share of the cake? ( Outside options which include jobs overseas may explain why the top income shares of some countries influence those of others.