From 1949 to 2013 - a period when the White House was roughly split between parties - the economy grew at an average annual rate of 3.33 percent, but growth under Democratic presidents averaged 4.35 percent and under Republicans, 2.54 percent. It’s a Democratic campaign consultant’s dream: a study from two respected academic economists concluding that, since the late 1940s, the economy has consistently performed better under Democratic presidents than Republican.