Stocks Enter ‘Danger Zone’—But Does It Really Matter?

​The S&P 500 has slipped below its 200-day moving average, a level that many traders see as a warning sign for further declines. But is breaking below a key moving average really the bearish omen it used to be? According to new research, it may not be as important as it once was.

Breaking a Moving Average Isn’t What It Used to Be
For decades, traders relied on technical signals like the 50-day and 200-day moving averages to determine market trends. Before the 1990s, dropping below these levels often signaled a prolonged downturn. But since the rise of exchange-traded funds (ETFs) and algorithmic trading, these signals have lost much of their predictive power.

The shift began in the early 1990s when broad-market ETFs became widely available, making it easier for investors to trade in and out of the market quickly. Before that, trading based on moving averages was difficult and expensive, requiring multiple transactions with high brokerage fees.

With today’s technology, millions of traders can react to moving average signals instantly, reducing their effectiveness. A study from Brandeis University professor Blake LeBaron found that not only have moving-average strategies stopped working in stocks, but they’ve also failed in currency markets, reinforcing the idea that once-profitable trading signals become weaker as more people try to exploit them.

A Changing Market Requires New Strategies
A study published in the Journal of Finance titled “Does Academic Research Destroy Stock Return Predictability?” found that stock indicators once thought to predict market outperformance became 58 percent less profitable after they were widely published. In other words, as soon as a strategy becomes common knowledge, its effectiveness starts to fade.

That lesson applies to moving averages today. While many traders still watch them, their predictive power isn’t what it used to be. The takeaway? Investors should be cautious about relying too heavily on any single technical indicator.

What’s Next for the Market?
While technical traders may see the S&P 500’s drop below its 200-day moving average as a red flag, history suggests that long-term investors shouldn’t panic. Fundamentals like corporate earnings, Federal Reserve policy, and economic growth still matter more than short-term technical signals.

The real challenge for investors is adjusting strategies as the market evolves. Moving averages may not be as predictive as they once were, but the ability to adapt remains crucial.