Since 1950, no other month has recorded a higher average return or has finished higher as often as December. Over the last 100 years, the Dow has averaged a gain of 1.55 percent in December, with gains 74 percent of the time.
It's even better the last two weeks of the year. For the S&P, the days during the Santa rally have gained 1.35 percent on average, with only one other seven-day period of the entire year sporting a better return. The seven days of Santa have been higher 77.6 percent of the time, making it the seven days of the year that are most likely to be higher