The focus on maintaining the current distribution of the tax burden is misguided because of income mobility, said Scott Hodge, president of the Tax Foundation, a Washington group that favors a simpler tax code with lower rates. He said more than 70 percent of people on the Internal Revenue Service's list of the 400 highest incomes between 1992 and 2008 made the list only once.
"Trying to tax any particular group is really trying to tax a snapshot of people as they move through it," Hodge said.