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Sunday, March 13, 2005

Wealth Inequality: It's a Gas 

Because they are simply not happy unless they're violating every law of man and nature, physicists have begun to take an interest in the workings of the dismal science. And based on the early findings to be presented this week in Kolkata, India, at the first-ever conference on the "econophysics" of wealth distribution, there's nothing surer: the rich get rich and the poor get laid off -- just as Gus Kahn and Richard Whiting told us back in 1921:
If you doubt it, ponder these numbers from the US, a country widely considered meritocratic, where talent and hard work are thought to be enough to propel anyone through the ranks of the rich. In 1979, the top 1% of the US population earned, on average, 33.1 times as much as the lowest 20%. In 2000, this multiplier had grown to 88.5. If inequality is growing in the US, what does this mean for other countries?

Almost certainly more of the same, if you believe physicists who are using new models based on simple physical laws to understand the distribution of wealth. Their studies indicate that inequality in market economies may be very hard to get rid of . . . .

In 1897, a Paris-born engineer named Vilfredo Pareto showed that the distribution of wealth in Europe followed a simple power-law pattern, which essentially meant that the extremely rich hogged most of a nation's wealth (New Scientist print edition, 19 August 2000). Economists later realised that this law applied to just the very rich, and not necessarily to how wealth was distributed among the rest.

Now it seems that while the rich have Pareto's law to thank, the vast majority of people are governed by a completely different law. Physicist Victor Yakovenko of the University of Maryland in College Park, US, and his colleagues analysed income data from the US Internal Revenue Service from 1983 to 2001.

They found that while the income distribution among the super-wealthy - about 3% of the population - does follow Pareto's law, incomes for the remaining 97% fitted a different curve - one that also describes the spread of energies of atoms in a gas (see graphic).

In the gas model, people exchange money in random interactions, much as atoms exchange energy when they collide. While economists' models traditionally regard humans as rational beings who always make intelligent decisions, econophysicists argue that in large systems the behaviour of each individual is influenced by so many factors that the net result is random, so it makes sense to treat people like atoms in a gas.

Yakovenko also found that the total income of those in the poorer part of the distribution did not change significantly with time after accounting for inflation. But incomes for those in the Pareto curve shot up nearly five times from 1983 to 2000, before declining with the US stock market crash of 2001 . . . .

"It suggests that any kind of policy will be very inefficient," says Yakovenko. It would be very difficult to impose a policy to redistribute wealth "short of getting Stalin", says Yakovenko, who will talk in Kolkata next week.

Macroeconomist Makoto Nirei at Utah State University in Logan, US, whose own work will be presented at the conference, is supportive of the physicists' work but he has reservations about how they model the exchange of money. "The model seems to me not like an economic exchange process, but more like a burglar process. People randomly meet and one just beats up the other and takes their money."

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