Executive Summary: “Political Polarization and Income Inequality” by Nolan McCarthy, Keith T. Poole, and Howard Rosenthal

            Few political scientists have sought to explain or highlight the links between economic inequality and political conflict in the United States.  This is due in part to the fact that traditionally, being rich or poor could not predict how one voted.  McCarty, Poole and Rosenthal show that income has become a powerful predictor of American political behavior.  Their paper explains the causes of party-income stratification or the rich vs. poor cleavage between parties by examining partisan identification from the National Election study done each year from 1952-2000 and Census data on household income.  With this data, the authors create a 7 point scale of partisanship ranging from ‘Strong Democrat’ to ‘Strong Republican.’ In this way, the authors also collect and compare data on demographic change and income shift.

In the period after WWII, the authors found that the richest fifth of the population was roughly as likely to identify as Republican as the poorest fifth.  However, in the 1990s, the wealthiest citizens are twice as likely to identify as Republican when compared with the least affluent.  Also among their results, the authors find that the flight of non-black Southerners between 1960 and 1996 from the Democratic party to the Republican party is marked by an increase in income among non-black Southerners over this period.  On the other hand, due to increasing numbers of single women in that same period, the percentages of women in the poorest segments have also increased.  To match their decline in income, women are now more likely to vote Democratic. Among African-Americans, who have seen their presence both at the bottom and top of society grow, the authors find that they are increasingly pro-Democratic since the numbers of African Americans in and entering poverty outstrips the growth rate of African-Americans improving their social standing.