Why does the stock market historically perform better during Democratic administrations?

Michael S asked: See links below for evidence demonstrating that the stock market performs better during Democratic administrations than Republican administrations. http://www.frbsf.org/images/pdfcharts/el98-19a.pdf http://www.frbsf.org/images/pdfcharts/el98-19a.pdf dpj5: Let’s see if what you’re saying is true: As I look over the data, I see that the two of the three periods with the biggest gains (33-36, 97-01, and 49-52) [...]