Tax Policy Center, A New Tax Bracket for Millionaires?, by Rachel Johnson & Jim Nunns:

The debate over extending the 2001–2003 tax cuts beyond 2010 has revolved around two options: extend all provisions for all taxpayers, and the president’s proposal to extend all provisions except those that apply only to high-income taxpayers. A third option has drawn attention: extend the 2001–2003 tax cuts fully for all taxpayers except those with income over $1 million. This paper explores alternate ways to structure an additional tax rate on millionaires (as defined by annual income, not wealth), but does not consider other alternatives, such as eliminating or reducing tax preferences, that would increase tax liabilities of millionaires without raising marginal tax rates.