Year-End Momentum: Why December Draws Traders to Recent Winners

Momentum investing rests on a simple observation: stocks that have done well over the past several months tend, on average, to keep doing well for a while, and laggards often keep lagging. Academic research documenting the effect dates back to the early 1990s, and it has since become a staple of quantitative and factor-based investing. As the calendar turns toward year end, a familiar claim resurfaces in stock roundups: that December is the strongest month for running these strategies, and that it is the time to chase the year's leaders.

The reasoning usually centers on tax-related selling. Many investors sell losing positions in December to realize capital losses before the year closes, which can push down the prices of underperformers. Fund managers, meanwhile, are sometimes thought to buy recent winners ahead of year-end reports so their portfolios look stronger on paper, a habit often called window dressing. Together, those forces are believed to widen the gap between winners and losers as the year ends.

The pattern has a known sequel, though. Once the calendar flips, the selling pressure eases, and beaten-down stocks sometimes rebound in January, which can hurt momentum portfolios still holding them. That reversal is one reason the seasonal effect is hard to rely on. Results also depend heavily on the period studied, how momentum is measured, and how often a portfolio is rebalanced, so a clean December advantage in one dataset may look much weaker in another.

The broader strategy carries its own risk. Momentum can suffer sharp drawdowns when markets change direction quickly, especially after a sell-off, when former losers rally hard and former leaders fall. Investors who concentrate in the most popular recent winners can end up holding the most crowded names just as sentiment shifts.

For anyone weighing a year-end momentum trade, the practical questions matter more than any list of tickers. How is the momentum signal defined? How large is the position relative to the rest of the portfolio? What is the plan if the trade reverses in early January? This is general market commentary, not personal financial advice, and any stock list should be checked against your own goals, time horizon and tolerance for losses.