Opponents point out that the tax code will become less progressive, exacerbating income inequality.

ECONOMIST: George Bush's tax agenda: Handing it back | The

But while the progressive income tax has continued to reduce inequality, it has not kept the gap in after tax income from fairly steadily widening over the 1987 to 2009 period, the researchers found.

FORBES: New Study Using IRS Tax Data Shows Rich Are Staying Richer, Poor Poorer

Progressive taxation is not the sole solution to extreme economic inequality in the US, but it can mitigate its effects.

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Because the tax code takes more from the top than from the bottom ("progressive, " in tax jargon), it significantly reduces inequality.

WSJ: The Numbers Behind the Tax Debate

The U.S. already has one of the most progressive tax systems in the world, so absent this red herring question about income inequality, taxing the wealthy would be an even tougher case to make.

FORBES: In Asking About Income Inequality, Obama Begins With The Wrong Question

Across emerging Asia political concerns about rising inequality are prompting reform, often in ways that echo the changes of the Progressive Era a century ago.

ECONOMIST: Why Asia, too, is becoming increasingly unequal

"With an increase of the millionaire's tax and a significant increase in the minimum wage, this budget takes strong steps to address income inequality, " said Michael Kink of the Strong Economy for All coalition of progressive groups.

WSJ: Cuomo, Legislature promise tax cuts in NY budget