Yesterday the S&P 500 reached 100 trading days without declining 1.5% or more. Since 1950, S&P 500 has accomplished this milestone just 42 times. Its longest streak began in November 1963 and ran until June 1965, a full 399 trading days. The shortest was 101 trading days in 1990. The biggest gain during a streak was 42.00% from July 1984 through January 1986 while the average gain in all previous streaks was 13.43% with gains occurring a whopping 92.9% of the time. Clearly, past streaks of low volatility were bullish.
However, when the streak ended, and the current streak will end eventually, the pendulum quickly swung to the opposite side with volatility quickly returning. One week after the previous 42 streaks ended, S&P 500 was down 92.9% of the time with an average loss of 2.09%. Two weeks later, gains remained scarce with S&P 500 up just 19.0% of the time.