January Effect

What Is the January Effect?

The January Effect is a perceived seasonal increase in stock prices during the month of January. Analysts generally attribute this rally to an increase in buying, which follows the drop in price that typically happens in December when investors, engaging in tax-loss harvesting to offset realized capital gains, prompt a sell-off.

Another possible explanation is that investors use year-end cash bonuses to purchase investments the following month. While this market anomaly has been identified in the past, the January effect seems to have largely disappeared as its presence became known.

Key Takeaways

  • The January Effect is the perceived seasonal tendency for stocks to rise in that month.
  • Since 1938, 29 out of 30 years of gains seen in January-February resulted in average yearly S&P 500 advances of 20%.
  • The January Effect is theorized to occur when investors sell winners to incur year-end capital gains taxes in December and use those funds to speculate on weaker performers.
  • Like other market anomalies and calendar effects, the January Effect is considered by some to be evidence against the efficient markets hypothesis.

Understanding the January Effect

The January Effect is a hypothesis, and like all calendar-related effects, suggests that the markets as a whole are inefficient, as efficient markets would naturally make this effect non-existent. The January Effect seems to affect small caps more than mid or large caps because they are less liquid.

Since the beginning of the 20th century, the data suggests that these asset classes have outperformed the overall market in January, especially toward the middle of the month. Investment banker Sidney Wachtel first noticed this effect in 1942. This historical trend, however, has been less pronounced in recent years because the markets seem to have adjusted for it.

Another reason analysts consider the January Effect less important as of 2021 is that more people are using tax-sheltered retirement plans and therefore have no reason to sell at the end of the year for a tax loss.

January Effect Explanations

Beyond tax-loss harvesting and repurchases, as well as investors putting cash bonuses into the market, another explanation for the January Effect has to do with investor psychology. Some investors believe that January is the best month to begin an investment program or perhaps are following through on a New Year's resolution to begin investing for the future.

Others have pontificated that mutual fund managers purchase stocks of top performers at the end of the year and eliminate questionable losers for appearance sake in their year-end reports, an activity known as "window dressing." This is unlikely, however, as the buying and selling would primarily affect large caps.

Year-end sell-offs also attract buyers interested in the lower prices, knowing the dips are not based on company fundamentals. On a large scale, this can drive prices higher in January.

Studies and Criticism

An ex-Director from the Vanguard Group, Burton Malkiel, the author of A Random Walk Down Wall Street, has criticized the January Effect, stating that seasonal anomalies such as it don't provide investors with any reliable opportunities. He also suggests that the January Effect is so small that the transaction costs needed to exploit it essentially make it unprofitable. It's also been suggested that too many people now time for the January Effect so that it becomes priced into the market, nullifying it all together.

Other researchers have found that January Effect still exists, but only for smaller-cap stocks, owing to a lack of liquidity and interest from investors.

What Is the January Effect in the Stock Market?

The January Effect is a purported market anomaly whereby stock prices tend to regularly rise in the first month of the year. Actual evidence of the January Effect is small, with many scholars arguing that it does not really exist.

Can You Make Money Exploiting the January Effect?

Unlikely. Even if the January Effect were real (it's probably not) and markets were to rise uncharacteristically each January, the fact that people may try to exploit can undermine its fruition.

What Is the January Barometer?

The January Barometer is a folk theory of the stock market that claims the returns experienced in January will predict the overall performance of the stock market for that year. Thus, a strong January would predict a strong bull market, and a down January a bear market. Actual evidence for this effect is scant.

Article Sources
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  1. CNBC. "Monthly Gains in January And February Historically Signal a 20% Average Market Advance for the Year." Accessed Feb. 2, 2022.

  2. College of William & Mary. "Yes, Wall Street, There Is a January Effect!," Page 1. Accessed Feb. 2, 2022.

  3. University of California, Berkeley-Econometrics Laboratory. "The Efficient Market Hypothesis and Its Critics," Page 63-64. Accessed Feb. 2, 2022.

  4. Haug, Mark, and Mark Hirschey. "The January Effect." Financial Analysts Journal, vol. 62, no. 5. 2006, pp. 78-88.

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