Most people do not construct a careful running tally of the parties’ long-term economic performance, of course. However, my 2008 book, “Unequal Democracy,” examined the economic record of Democratic and Republican presidents since the late 1940s using official tabulations from the Bureau of Economic Analysis, the Bureau of Labor Statistics, and the Census Bureau’s Historical Income Tables. I found that GNP growth was generally stronger, unemployment lower, and incomes more equal under Democratic presidents than when Republicans were in the White House. The real incomes of middle-class and working-poor families grew much faster under Democrats, on average, even after allowing for a variety of possible confounding factors — long-term trends in growth, family structure and labor force participation, world oil prices, and “trickle-down” effects of previous growth.

Newly updated Census Bureau tabulations through 2011 continue to show substantial partisan disparities in income growth rates over the entire postwar period. (These tabulations include revised data from previous years as well as new data from 2006 through 2011.) Average income growth under Democratic presidents has been fairly robust across the income spectrum, while growth under Republican presidents has been much weaker and has mostly benefited affluent families. Over more than six decades, the average incomes of middle-class families have grown more than twice as fast under Democratic presidents as they have under Republican presidents. The average incomes of working poor families have grown nine times faster under Democrats.

http://www.salon.com/2012/11/02/want_a_strong_economy_vote_democrat/