Since at least 1950, the year following US midterm elections has always seen the S&P 500 rise. During this 70-year period there have been 10 elections with a Republican president, and eight with a Democratic one. The best year for equities was 1955 (Eisenhower) when they gained about 30%, while the weakest year was 1987 (Reagan) when equity returns were barely positive. The average gain is about 15%.