1. Using a panel of tax returns from 1999 through 2007, this report finds that nearly 60 percent of households in the bottom quintile in 1999 are in a higher quintile in 2007 (and more than 16 percent are in one of the top two quintiles in 2007). Roughly 40 percent of tax returns in the top quintile in 1999 are in a lower quintile in 2007 (and more than 14 percent moved down by two or more quintiles by 2007).
2. The report also examines the persistence/transience of millionaires and finds that this group of taxpayers, which has been the focus of millionaire surtaxes among some states and some tax policy proposals at the federal level, is highly transient. Roughly 50 percent of those taxpayers who were millionaires at some point during the 1999 through 2007 period attained this status just once. In contrast, only 6 percent of this group of taxpayers were millionaires in all nine years (see chart above).
3. Millionaires are a highly transient group of taxpayers, and it appears that the realization of capital gains is at least one explanation. This income source tends to be lumpy and periodic and is a major explanation for why taxpayers reach millionaire status.