How Likely Is the S&P 500 to Be Positive on Any Random Day?

The S&P 500 tracks 500 leading U.S. companies, making it a reliable gauge of market health. Whether you’re a day trader, long-term investor, or just curious about market behavior, understanding the likelihood of a positive day can shape your strategy.

A higher probability of gains might encourage optimism, while knowing the risks can help you prepare for volatility. Our analysis, confirmed through backtesting with SPY, shows that the market tilts slightly in favor of positive days—a fact that could influence everything from trading decisions to portfolio management.

Table of contents:

The Numbers: A 54% Chance of a Positive Day

Historical data from 1993 to today reveals that the S&P 500 closes higher than the previous day on approximately 54% of trading days. This figure comes from analyzing daily price changes over multiple periods, with results ranging from 53% to 55%. For instance:

1996–2016: 53.3% of days were positive.
2016–2021: 54.9% of days saw gains.

Over periods of decades, the numbers are very similar – even in bear markets, perhaps surprisingly for many. Please also read our take on the anatomy of a bear market.

We backtested SPY, the popular ETF that mirrors the S&P 500, from its inception until today. While short-term periods, like a single month in 2025, may show slightly higher or lower percentages (e.g., 57.89% for April 7–May 5, 2025), the long-term average of 54% provides a reliable baseline.

The results are summarized in this table:

		%
# Trading Days	8120
# Up days	4376	53.89
# Down days	3744	46.11

This slight edge over 50% reflects the market’s long-term upward bias, driven by economic growth, corporate earnings, productivity gains, and investor confidence. However, the remaining 46% of down days remind us that volatility is part of the game.

What Influences the S&P 500’s Daily Moves?

Several factors can sway whether the S&P 500 ends a day up or down:

Economic Conditions: Bull markets, characterized by optimism and growth, often see more positive days, while bear markets tilt toward losses.
Corporate Earnings: Strong earnings reports from S&P 500 companies can boost the index, while disappointing results may drag it down.
Global Events: Geopolitical tensions, interest rate changes, or unexpected news (e.g., Federal Reserve announcements) can spark volatility.
Market Sentiment: Investor psychology, driven by fear or greed, plays a big role in daily swings.

While the 54% positivity rate is a historical average, these factors mean no single day is guaranteed to follow the trend.

For example, during turbulent periods like the 2008 financial crisis, down days were more frequent, while strong recovery years like 2020–2021 saw higher-than-average positive days.

How Investors Can Use This Data

Knowing the S&P 500 has a 54% chance of a positive day can inform your approach to the market. Here are three practical ways to apply this insight:

Set Realistic Expectations: A 54% probability means the market leans positive but isn’t a sure bet. Avoid overconfidence and plan for both up and down days.
Optimize Trading Strategies: Day traders might use this data to fine-tune entry and exit points, focusing on momentum or short-term trends.
Stay Disciplined: Long-term investors can take comfort in the market’s upward bias but should diversify and stick to their plan, regardless of daily fluctuations.

Limitations and Considerations

Here are key limitations to keep in mind:

Timeframe Variability: Short-term periods may deviate from the 54% average due to market conditions. For instance, a volatile month in 2025 could see fewer positive days.
No Guarantee of Magnitude: A positive day doesn’t always mean significant gains. The S&P 500’s average daily move (up or down) is about 0.73%, so many positive days are modest.
External Shocks: Unexpected events, like economic policy shifts or global crises, can disrupt historical patterns.

To stay informed, monitor real-time data from sources like Investing.com or follow market analysts on platforms like X for timely updates.

Conclusion: A Slight Edge in a Complex Market

The S&P 500’s 54% likelihood of a positive day offers a fascinating glimpse into market behavior. Backed by historical data and confirmed through SPY backtesting, this statistic highlights the market’s gentle upward tilt while reminding us of its inherent risks.