www.princeton.edu/~mwatson/papers/Presidents_Blinder_Watson_July2014.pdf.

“We begin in Section 1 by documenting this fact, which is not at all “stylized.” The U.S. economy not only grows faster, according to real GDP and other measures, during Democratic versus Republican presidencies, it also produces more jobs, lowers the unemployment rate, generates higher corporate profits and investment, and turns in higher stock market returns.

Indeed, it outperforms under almost all standard macroeconomic metrics. By some measures, the partisan performance gap is startlingly large–so large, in fact, that it strains credulity, given how little influence over the economy most economists (or the Constitution, for that matter) assign to the President of the United States.”