You’ll see this question posed on talk shows and in blog post comments: why do Americans vote in a way that is contrary to economic self-interest? Why do Americans support policies that shift capital to the richest one percent of the population?

Some think it’s the myth of American individualism: that anyone can be a billionaire – just work hard and riches will be yours. Malcolm Gladwell shut the door on that myth with his book, Outliers, but most Americans don’t read.

Mother Jones (March-April 2011 issue) has pulled together “eight charts that explain everything that’s wrong with America.”

Seeing this chart — the difference between perception, preference and actual wealth distribution — was like having my head slammed up against a car door. The chart is derived from research conducted (pdf) by Michael L. Norton (Harvard Business School) and Dan Ariely (Duke University) for Perspectives on Psychological Science. The authors note that most scholars peg wealth inequality in the U.S. at historic highs, greater than the roaring 20s; the estimate was that the top 1% hold almost 50% of the nation’s wealth.

Their nationally representative sample of 5,522 (December 2005) began with a recap of what wealth means:

Wealth, also known as net worth, is defined as the total value of everything someone owns minus any debt that he or she owes. A person’s net worth includes his or her bank account savings plus the value of other things such as property, stocks, bonds, art, collections, etc., minus the value of things like loans and mortgages.

And then the researchers asked what they considered a “just” distribution of wealth. When faced with three unlabled pie charts, one “perfectly equal”, one representing wealth distribution in the the US and one the distribution in Sweden, 92% of the respondents preferred Sweden. This preference crossed party lines and gender. Look at the three charts and you will understand why.

Next task: draw the perfect distribution and the one that you think represents the U.S. today. The respondents understood that America was not Sweden, they simply had no idea that the top quintile (20%) of Americans control the vast majority of the nation’s wealth:

[R]espondents vastly underestimated the actual level of wealth inequality in the United States, believing that the wealthiest quintile held about 59% of the wealth when the actual number is closer to 84%.

I’d like to know how they thought wealth was distributed inside the top quintile. The top 5% holds more than half the nation’s wealth.

In picturing the ideal wealth distribution, party affiliation did play a role: “women, Kerry voters, and the poor desired relatively more equal distributions than their counterparts.” However, the researchers note that the more “striking” finding was the level of consensus:

All groups – even the wealthiest respondents – desired a more equal distribution of wealth than what they estimated the current United States level to be, while all groups also desired some inequality – even the poorest respondents. In addition, all groups agreed that such redistribution should take the form of moving wealth from the top quintile to the bottom three quintiles.

These charts and the others featured at Mother Jones reveal basic economic inequality, inequality that helps explain why the United States ranks in the bottom third on the world’s list of countries by income inequality, based upon the Genie coefficient (excluding countries with no Genie coefficient). [Yes, I know that wealth inequality and income inequality are not the same thing. But the former rests soundly upon the latter.]

What is the Genie coefficient? Based on mathematical analysis from the early 20th century, it is a measure of the inequality of a distribution — any distribution. It has been criticized because it measures income, not returns on investment or food stamps. For most advanced economies, the Gini coefficient for income is pretty low: Sweden, for example, is 0.23; the European Union is 0.307. The United States is 0.45 (2007 data).

And income inequality is real, too. Here are some numbers from the Institute for Policy Studies:

• Percentage of U.S. total income in 1976 that went to the top 1% of American households: 8.9.
• Percentage in 2007: 23.5
• Only other year since 1913 that the top 1 percent’s share was that high: 1928
• Combined net worth of the Forbes 400 wealthiest Americans in 2007: $1.5 trillion
• Combined net worth of the poorest 50% of American households: $1.6 trillion

If you can’t see the inequality, if the picture you hold in your mind is so vastly different from reality, then it should be no surprise when you vote against your own economic self-interest.