September Slump? New Research Shows Seasonal Market Myths Don’t Hold Up

For a long time, people have thought of September as the “worst month” for markets, with traders often preparing themselves for seasonal drops as if they were guaranteed. However, new research shows that these calendar-driven narratives are more superstition than signal, and holding on to them could even cost investors ￰0￱ Myth of September Weakness On September 3, investment services provider Market Radar sought to dismantle the popular “Sell in September” ￰1￱ a detailed post, the platform’s analysts highlighted that most seasonality charts rely on averages, which are easily skewed by outliers such as crashes or extraordinary rallies. However, when measured by medians, which, according to Market Radar, is a better gauge of typical returns, the picture changes dramatically.

September’s median return, for example, is only –0.3%, far from the narrative of a guaranteed ￰2￱ firm stressed that even with median-based analysis, no month shows consistent predictive ￰3￱ rates across all months hover near a coin flip, with December reaching only ~59% and November dropping to ~41%. “If seasonality worked, you’d expect win rates well above 50%. Instead, most months are indistinguishable from random guessing,”