Do tax cuts increase the incentive to work?

Art Laffer is laughing:

Over the past half century, the top marginal tax rate has fallen from 91 percent in the 1950s and early 1960s to 35 percent today.  Thus, the amount a person gets to keep at the margin has risen from 9 percent to 65 percent, that is, by a factor of 7.2.  If the elasticity of taxable income with respect to 1-t is one, as some studies find for high-income taxpayers, then the incomes of the rich would have risen by a factor of 7.2 as well.  If the elasticity is one-half, then their incomes would have risen by a factor of 2.7.  In either case, the change in pretax income attributable to the tax cuts is substantial.