January Effect: What It Is and Is It Good for Investors?

By Brian O'Connell · December 13, 2022 · 6 minute read

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January Effect: What It Is and Is It Good for Investors?

The January Effect is a term that some financial market analysts use to classify the first month as one of the best-performing months, stock-wise, during the year. Analysts and investors who believe in this phenomenon claim that stocks have large price increases in the first month of the year, primarily due to a decline in share prices in December. Theoretically, following the dip in December, investors pour into stocks and boost prices in January.

However, many analysts claim that the January Effect and other seasonal anomalies are nothing more than market myths, with little evidence to prove the phenomenon definitively. Nonetheless, it may be helpful for investors to understand the history and possible causes behind the January Effect.

What Is the January Effect?

As noted above, the January Effect is a phenomenon in which stocks supposedly perform well during the first month of the year. The theory is that many investors sell holdings and take gains from the previous year in December, which can push prices down. This dip supposedly creates buying opportunities in the first month of the new year as investors return from the holidays. This buying can drive prices up, creating a “January Effect.”

Believers of the January Effect say it typically occurs in the first week of trading after the New Year and can last for a few weeks. Additionally, the January Effect primarily affects small-cap stocks more than larger stocks because they are less liquid.

To take advantage of the January Effect, investors can either buy stocks in December that are expected to benefit from the January Effect or buy stocks in January when prices are expected to be higher due to the effect. Investors can also look for stocks with low prices in December, but have historically experienced a surge in January, and buy those stocks before the increase.

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What Causes the January Effect?

Here are a few reasons why stocks may rise in the first month of the year.

Tax-Loss Harvesting

Stock prices supposedly decline in December, when many investors sell certain holdings to lock in gains or losses to take advantage of year-end tax strategies, like tax-loss harvesting.

With tax-loss harvesting, investors can lower their taxable income by writing off their annual losses, with the tax timetable ending on December 31. According to U.S. tax law, an investor only needs to pay capital gains taxes on their investments’ total realized gains (or losses).

For example, suppose an investor owned shares in three companies for the year and sold the stocks in December. The total value of the profit and loss winds up being taxed.

Company A: $20,000 profit
Company B: $10,000 profit
Company C: $15,000 loss

For tax purposes, the investor can tally up the total investment value of all three stocks in a portfolio — in this case, that figure is $15,000 ($20,000 + $10,000 – $15,000). Consequently, the investor would only have to pay capital gains taxes on $15,000 for the year rather than the $30,000 in profits.

If the investor still believes in Company C and only sold the stock to benefit from tax-loss harvesting, they can repurchase the stock 30 days after the sale to avoid the wash-sale rule. The wash-sale rule prevents investors from benefiting from selling a security at a loss and then buying a substantially identical security within the next 30 days.

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A Clean Slate for Consumers

U.S. consumers, who have a robust say in how the American economy will perform, traditionally view January as a fresh start. Adding stocks to their portfolios or existing equity positions is a way consumers hit the New Year’s Day “reset” button. If retail investors buy stocks in the new year, it can result in a rally for stocks to start the year.

Moreover, many workers may receive bonus pay in December or January may use this windfall to buy stocks in the first month of the year, adding to the January Effect.

Portfolio Managers May Buy In January

Like consumers, January may give mutual fund portfolio managers a chance to start the year fresh and buy new stocks, bonds, and commodities. That puts managers in a position to get a head start on building a portfolio with a good yearly-performance figure, thus adding more investors to their funds.

Additionally, portfolio managers may have sold losing stocks in December as a way to clean up their end-of-year reports, a practice known as “window dressing.” With portfolio managers selling in December and buying in January, it could boost stock prices at the beginning of the year.

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Is the January Effect Real?

The January Effect has been studied extensively, and there is evidence to suggest that it is somewhat real. Studies have found that small- and mid-cap stocks tend to outperform the market during January because they are less liquid.

But some analysts note that the effect has become less pronounced in recent years due to the rise of tax-advantaged investing accounts, like 401(k)s and individual retirement accounts (IRAs). Investors who use these accounts may not have a reason to sell in December to benefit from tax-loss harvesting. Therefore, while the January Effect may be somewhat real, its impact may be more muted than in the past.

January Effect and Efficient Markets

However, many investors claim that the January Effect is not real because it is at odds with the efficient markets hypothesis. An efficient market is where the market price of securities represents an unbiased estimate of the investment’s actual value.

Efficient market backers say that external factors — like the January Effect or any non-disciplined investment strategy — aren’t effective in portfolio management. Since all investors have access to the same information that a calendar-based anomaly may occur, it’s impossible for investors to time the stock market to take advantage of the effect. Efficient market theorists don’t believe that calendar-based market movements affect market outcomes.

The best strategy, according to efficient market backers, is to buy stocks based on the stock’s underlying value — and not based upon dates in the yearly calendar.

History of the January Effect

The phrase “January Effect” is primarily credited to Sydney Wachtel, an investment banker who coined the term in 1942. Wachtel observed that many small-cap stocks had significantly higher returns in January than the rest of the year, a trend he first noticed in 1925.

He attributed this to the “year-end tax-loss selling” that occurred in December, which caused small-cap stocks to become undervalued. Wachtel argued that investors had an opportunity to capitalize on this by buying small-cap stocks during the month of January.

However, it wasn’t until the 1970s that the notion of a stock rally in January earned mainstream acceptance, as analysts and academics began rolling out research papers on the topic.

The January Effect has been studied extensively since then, and many theories have been proposed as to why the phenomenon may occur. These include ideas discussed above, like tax-loss harvesting, investor psychology, window-dressing by portfolio managers, and liquidity effects in stocks. Despite these theories, the January Effect remains an unexplained phenomenon, and there is a debate about whether following the strategy is beneficial.

The Takeaway

Like other market anomalies and calendar effects, the January Effect is considered by some to be evidence against the efficient markets hypothesis. Nevertheless, there is evidence that the stock market does perform better in January, especially with small-cap stocks.

Whether one believes in the January Effect or not, it’s always a good idea for investors to use strategies that can best help them meet their long-term goals.

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Tax Information: This article provides general background information only and is not intended to serve as legal or tax advice or as a substitute for legal counsel. You should consult your own attorney and/or tax advisor if you have a question requiring legal or tax advice.


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