August is often viewed as a dangerous month for stock markets, but more than 200 years of data tell a different story. Historically, stocks typically gain during the month, and volatility sits well below average.
The idea of an August slump has persisted on Wall Street for decades. Traders and investors often cite lower trading volumes and summer vacations as reasons for caution. Yet the numbers do not support that narrative.
Market data shows that the S&P 500 and its predecessors have posted positive returns in August roughly 60% of the time. The average gain for the month is modest but positive.
Volatility readings tend to be lower in August compared to other months. The Cboe Volatility Index, or VIX, often sits at levels well below its long-term average during this period.
The belief in an August slump may stem from a few notable exceptions. Major selloffs in August 2011 and 2015 left a strong impression on market participants.
These outlier events are often cited as evidence of a recurring pattern. However, they are statistically rare and do not reflect the broader historical trend.
Wall Street’s tendency to repeat the August slump myth may be driven by cognitive bias. Confirmation bias leads traders to remember bad Augusts more vividly than good ones.
The media also plays a role by highlighting downturns during slow news periods. This reinforces the perception that August is inherently risky, despite the facts.
For long-term investors, the data suggests August is not a month to fear. Staying invested and ignoring seasonal myths typically yields better outcomes.
The real risk may lie in acting on these unfounded beliefs. Timing the market based on calendar myths can lead to missed gains and unnecessary losses.
