It's fascinating that many Americans intuitively understood the outrage and frustration that drove Egyptians to protest at Tahrir Square, but don't comprehend similar resentments that drive disgruntled fellow citizens to "occupy Wall Street."

There are differences, of course: the New York Police Department isn't dispatching camels to run down protesters. Americans may feel disenfranchised, but we do live in a democracy.

Yet my interviews with protesters in Manhattan's Zuccotti Park seemed to rhyme with my interviews in Tahrir earlier this year. There's a parallel sense that the political/economic system is tilted against the 99 percent. Al Gore described them as a "primal scream of democracy."

The frustration in America isn't so much with inequality in the political and legal worlds, as it was in Arab countries. Here the critical issue is economic inequity. The CIA's ranking of countries by income inequality shows the U.S. is more unequal a society than Tunisia or Egypt.

Three factoids underscore that inequality: The 400 wealthiest Americans have a greater combined net worth than the bottom 150 million. The top 1 percent of Americans possess more wealth than the bottom 90 percent. In the Bush expansion from 2002 to 2007, 65 percent of economic gains went to the richest 1 percent.

There's a growing sense that lopsided outcomes are a result of tycoons' manipulating the system and lobbying for loopholes. Of the 100 highest-paid chief executives in the U.S. in 2010, 25 took home more pay than their company paid in federal corporate income taxes, according to the Institute for Policy Studies.

Living under Communism in China made me a fervent enthusiast of capitalism. I believe that over the last couple of centuries banks have enormously raised living standards in the West by allocating capital to more efficient uses. But anyone who believes in markets should be outraged that banks rig the system so that they enjoy profits in good years and bailouts in bad years. The banks have gotten away with privatizing profits and socializing risks, and that's just another form of bank robbery.

Economists used to believe that we had to hold our noses and put up with high inequality as the price of robust growth. But more recent research suggests the opposite: inequality not only stinks, but also damages economies.

In his new book, "The Darwin Economy," Robert H. Frank of Cornell University cites a study showing that among 65 industrial nations, the more unequal ones experience slower growth on average. And countries grow more rapidly when incomes are more equal, and slow down when incomes are skewed.

That's certainly true of the U.S. We enjoyed considerable equality from the 1940s through the 1970s, and growth was strong. Since then inequality has surged, and growth has slowed.

One reason may be that inequality is linked to financial distress and financial crises. There is mounting evidence that inequality leads to bankruptcies and to financial panics. It also leads to early deaths and more divorces.

Some critics think that Occupy Wall Street is simply tapping into the public's resentment and covetousness, nurturing class warfare. Sure, there's a dollop of envy. But inequality is also a cancer on our national well-being.