In 1955, the year April 15 became the IRS tax-filing deadline, America's top 400 taxpayers paid three times more of their income in taxes than the top 400 of 2006, the most recent year with IRS data available.

According to a new Tax Day report that we co-authored, if the top 400 of 2006 had paid taxes at 1955 rates, the federal treasury would have collected -- from these 400 taxpayers alone -- an additional $35.9 billion more in revenue in 2006.