What this diagram shows is the percentage growth in income under a Republican and a Democratic administration over the course of a four year Presidential term. It gives the lie to the common assertion that it doesn’t matter to the ordinary citizen who is in power. Apparently the economy doesn’t just ‘keep on truckin’: Democrats actually generate more income growth and also shift wealth to the poor. Republicans tend to shift wealth to the rich and still generate less extra wealth for the rich than Democrats do.
Obviously the economy may not be the major determinant of one’s voting decision. What Bartels’ plot shows is that Democrats’ assertions that they help the common man are more than hot air. The different policy agendas of the major US parties really do make a significant difference to both wealth generation and equality within the nation.
For a more detailed analysis, check out Larry Bartels’ discussion on Rodrik’s blog.