The stock market gains this year are shaping out to be the best in well over a decade. With September heading toward its close, the S&P 500 is on track for its best first three quarters since 1997.
The index has soared 19.4 percent this year, but how long will the rally continue?
Since 1928, the market has been up this much only 14 other times. In 10 of those instances, the S&P 500 continued to climb in the last quarter of the year, posting an average gain of 6.9 percent.
When the market was down, however, it was down big. Consider two of the last four times the S&P 500 fell in Q4, both of which took place during crash years: Q4 1987 (-23%) and Q4 1929 (-29%).
—BY CNBC's Giovanny Moreano. Follow him on Twitter: