The rally in US stocks slowed last month as the S&P 500 Index ended January up a modest 1.6%, following a whopping 8.9% gain this past November and 4.4% gain in December.1 With US equities off to a more tempered start in 2024, discerning investors are left to wonder about two well-known phenomena regarding the first month of the year: the January effect and the January barometer.
What have equity returns the first month of the year historically looked like? Is stock performance in January indicative of what performance will be for the full year? The January effect and January barometer shed light on these questions. But do they create investment opportunities? Probably not.
What is the January effect?
On average, US equity returns have tended to be strongest in January, compared to the other 11 months. The trend has been especially prevalent among small-cap stocks.2 Several theories attempt to explain why, including the impact of year-end tax loss harvesting, the flow of funds in the new year, and investor psychology. Interestingly, although the January effect was seen throughout the 20th century, it has weakened substantially in recent decades.