Going back to 1950, S&P 500 has enjoyed 15 streaks of consecutive monthly gains lasting 7 or months. The most recent streak came to an end with September’s full-month decline. The longest consecutive monthly winning streak lasted 11 months and occurred twice, from September 1953 to July 1954 and from March 1958 to January 1959. S&P 500’s average gain during these monthly winning streaks has been a solid 25.86%. The smallest gain was 9.09% ending March 1993 while the largest was a whopping 53.53% ending in April 1983. When past streaks ended, S&P 500 performance following tended to be mixed and rather tepid compared to its performance during the winning streak. The month after the streak ends, 3-month, 6-month and 1-year after performance appears in the table above.