A central contention of conservatives who cut taxes of those with high incomes while simultaneously reducing social insurance programs is that these measures are not undertaken to help the rich, but to help everyone by putting in place incentives that will accelerate economic growth. For example, Greg Mankiw, former head of President Bush's Council of Economic Advisors, wrote to the New York Times on June 5 that "the data show that the rich take a rising share of income when economic growth is booming…. Their share declines when the economy hits hard times…."

Do the data support the idea that a bigger share of income for the rich results in more rapid economic growth? For the United States since 1959, the answer is unambiguously "no!" (Brad DeLong looks at data from 1913 and comes to the same conclusion here)

Since the early 1980's more and more income has been concentrated at the top of the income distribution, but there has been no significant change in the rate of economic growth.

Conservatives like Mankiw propose that the relationship between income concentration and economic growth is positive, as illustrated by the upward sloping line in the figure below. But the actual data points for the US from 1959 to 2002 lie nowhere near Mankiw's line. In fact, they exhibit no significant relationship at all.

If we smooth the data a bit by taking five year moving averages we can see the evolution of income concentration and economic growth more clearly. (A moving average calculates the share of income of the top 1 percent and the growth of real GDP for 1961 as the averages of these numbers for 1959-1963; for 1962, the averages are for 1960-1964, and so on). As we see below, the share of income of the top 1 percent remained in a narrow range from 1959 through the early 1980s. During that time, the rate of economic growth rose and fell without any connection to income concentration. Since the early 1980s income has become more and more concentrated at the top. Income growth has not responded at all to this growing concentration of income. There is no evidence at all for an upward slope to the data points in the figure below.

Like so much else in conservative ideological rhetoric, the claim that there is a trade-off between fairness and growth is uncorroborated by the facts. Of course we must take care that policy does not distort incentives to hurt the economy. But there is no evidence that the tax cuts for the rich undertaken in the Reagan and Bush administrations have done anything at all to accelerate growth, nor that the Clinton tax increases came at the expense of economic growth. It's a smoke screen, folks. The real agenda is for the rich to pig-out.

Bernard Wasow is a senior fellow at The Century Foundation.