10-Did the United States grow more unequal while Republicans were in power? It sounds crude, but Princeton political scientist Larry Bartels has gone a long way toward proving it. Bartels looked up income growth rates for families at various income percentiles for the years 1948 to 2005, then cross-checked these with whether the president was a Republican or a Democrat. He found two distinct and opposite trends. Under Democrats, the biggest income gains were for people in the bottom 20th income percentile (2.6 percent). The income gains grew progressively smaller further up the income scale (2.5 percent for the 40th and 60th percentiles, 2.4 percent for the 80th percentile, and so on). But under Republicans, the biggest income gains were for people in the 95th percentile (1.9 percent). The income gains grew progressively smaller further down the income scale (1.4 percent for the 80th percentile, 1.1 for the 60th percentile, etc.).
Two other observations are worth making:
1) In all income categories except the 95th percentile, income growth rates under Democratic presidents exceeded income growth rates under Republican ones. That suggests greater income equality can coexist with (or even help create) greater prosperity.
2) The 95th percentile fared about the same under Democrats and Republicans. (This chart shows it doing slightly better under Democrats, but the margin of error erases the Democrats’ advantage.) Bartels’ party-based interpretation of income inequality can’t address the Great Divergence, Part 2—the stratospheric rise in incomes at the very top—because for this group, it doesn’t matter much whether a Democrat or a Republican inhabits the White House. Political scientists Jacob Hacker and Paul Pierson, of Yale and Berkeley, respectively, argue that the apparently nonpartisan solicitude Democrats and Republicans express toward the rich is the result of a massive increase in Washington’s corporate lobbying sector since the 1970s—and that the growing power of big business in Washington has been a major contributor to the Great Divergence.