The Jobs and Growth Tax Relief Reconciliation Act of 2003 (JGTRRA) significantly changed tax policy by cutting long-term capital gains tax rates and taxing dividend income at the same rates as long-term capital gains. Following the reduction in the tax disadvantage of dividends, investors gravitated toward dividend-paying investments—especially high-income investors who previously had faced the highest tax rates on dividends. The behavior of investors before and after the passage of JGTRRA suggests that they divide into “clienteles” based on dividend payouts when the tax disadvantage of dividends varies across investors. Policymakers therefore need to build a proper appreciation of investor behavior, particularly among affluent households, into their thinking about any tax reform proposal affecting capital income. If dividend clientele effects are ignored, estimates of the revenue that can generated by changes in capital tax rates will be off-base.