This paper estimates the elasticity of taxable income to the net-of-tax share using a panel of tax returns that follows a random sample of taxpayers from 1999 to 2005, spanning the EGTRRA 2001 and JGTRRA 2003 tax changes. Results suggest that the elasticity of taxable income to the current year's net-of-tax share lies between 0.3 and 0.4 overall, and that the elasticity of a broader measure of income falls between 0.1 and 0.2 overall, with substantially higher elasticities for taxpayers reporting income in excess of $500,000. (Contains 6 tables and 24 footnotes.)