September has a richly deserved reputation as the worst month for the stock market. For instance, this month marked the start of the 2008 financial crisis. As Ryan Detrick, senior market strategist at LPL Financial, put it: “September is the banana peel month.”
But in 2018, if the past is any guide, things may go better. There is an exception to September’s rotten record: When the S&P 500 is up in the five prior months—and that’s the case this year—September is up an average 2.3%, Detrick said.
Otherwise, the month’s performance is pretty dismal. Maybe it’s due to investors coming home from summer vacation eager to dump what they see as losers. Who knows? But since 1928, according to Bespoke Investment Group, the S&P has averaged a 1.05% decline.
Worse, when stocks roll into September already limping, they really get creamed. In years when stocks are down through August, the September drop is an average 3.43%. And when the index is off 5% or more through August, September piles on with a 3.78% decline.
And when the S&P has been positive May through August, September has been up as well, averaging a 0.29% gain. During the May-August span in 2018, the S&P rose more than 9% for its best summer since 2009. When the S&P has been down during the summer months, the S&P has averaged a September dip of 3.23%.
As Bespoke explained the phenomenon: “While September has indeed been the worst month of the year for stocks, the negativity usually comes during years when the market is already struggling entering the month.”
And this year, the economy is doing quite well. That’s not to say that the month won’t see some volatility, which it also is known for, LPL’s Detrick noted. Indeed, he went on, “we’d be surprised if volatility didn’t pick up given midterm years tend to see big moves in the months leading up to the November election.”