With markets off to a rocky start on Tuesday, it's worth noting that September has historically been the worst month for equities. Dating back to 1950, the S&P 500 has declined by an average of 0.49 per cent in the month. However, as BMO Nesbitt Burns senior economist Robert Kavcic points out in a research note, September has fared better during the current bull run. Since 2010, the calendar's final four months have "been a clear positive standout, with September actually improving meaningfully over a very difficult August."