S&P 500 Seasonality: The Chart That Sends Shivers Down Spines In September, But With Peculiar Twist
In the world of financial markets, September brings a sense of dread that’s hard to shake. It’s the month that has Wall Street on edge, and for good reason.
A recent in-depth seasonality analysis on the S&P 500 Index conducted by Bank of America analyst Stephen Suttmeier, CFA, paints a rather chilling picture.
Spanning nearly a century of market data dating back to 1928, September emerges as the worst month of the year for the U.S. stock market.
The statistics are a stark reminder: September has witnessed the S&P 500 closing positively only 44% of the time, a revelation that already points to a rather unfavorable track record. Furthermore, the average return in September shows a decline of 1.2%, the worst than in other month of the year.
Even when narrowing the lens to focus on last quarter of a century, September’s bearish sentiment remains intact. The data reflects an average decline of 0.53%, the highest among all the months.
Chart: Monthly Returns Of S&P 500 Index (1998-2023)
Why There’s A Glimmer Of Hope In 2023
According to the Bank of America study, when the S&P 500 posts year-to-date gains through August, September has historically shown better performance, with positive returns occurring 49% of the time. Yet these gains are relatively modest, with an average return of 0.08%.
Conversely, when the S&P 500 is in the red year-to-date through August (although this isn’t the case for 2023), September has historically struggled. It has seen positive returns only 34% of the time, and these returns are notably negative, averaging a negative 3.61%.
Delving deeper into the data, an exceptionally strong rally of 20% or more in the S&P 500 year-to-date through August might not bode well for September and the rest of the year. In this scenario, September shows positive returns in only 45% of cases, with an average return of negative 0.67%
There is a silver lining. The most robust September and subsequent year-end returns tend to occur when the S&P 500 registers more moderate gains of 10% to 20% year-to-date through August.
Out of the 23 instances when the S&P 500 had posted year-to-date gains ranging between 10% and 20% through August, it exhibited positive performance in an impressive 65% of those cases. The average return during these instances amounted to a noteworthy 0.77%.
In 2023, the SPDR S&P 500 ETF Trust (NYSE:SPY) has indeed delivered a year-to-date return of 17.4% through August, fitting snugly into this historically favorable “sweet spot.”
Statistic
S&P 500
September returns
for all years
(since 1928)September returns
when the S&P 500
is up 10%-20% YTD
through AugustSeptember returns
when the S&P 500
is up 20%+ YTD
through August
Average
-1.16%
0.77%
-0.67%
Median
-0.49%
1.49%
-0.65%
% of time up
44.21%
65.22%
45.45%
Max
14.40%
4.84%
8.31%
Min
-29.94%
-8.54%
-12.35%
Std Dev
5.74%
2.86%
5.50%
#obs
95
23
11
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