The S&P 500 Just Did This for the 21st Time in the Past 100 Years. History Is Clear About What the Next 12 Months Could Look Like.

The S&P 500 (^GSPC 0.43%) in November wrapped up an impressive streak that happens on average only once every five years. It posted its seventh consecutive positive monthly return. Then the index lost just 0.05% in December and rose in January. Before the final closing bell, February was looking like a down month.

A seven-month streak is impressive. And it warrants a deeper look to see whether this is any kind of momentum signal. Do gains at that point tend to continue, or is there typically a mean reversion that investors should watch out for?

Image source: Getty Images.

The latest streak, which went from May to November 2025, was the 21st time that the S&P 500 has gone seven straight positive months (or longer). To assess the potential here, I looked at the past 20 times this has happened and calculated the S&P 500’s returns over the next 12 months. That time frame would start following the completion of the seventh positive month in a row.

Here’s what the data looks like:

Data source: Yahoo! Finance.

For the most part, these streaks tend to be pretty spread out and have a wide range of subsequent 12-month returns. Some of them occurred during periods of peak market stress, but there’s really no discernible trend as to when they could occur.

But when you break down the numbers themselves, here’s what it looks like:

Data source: Yahoo! Finance.

After seven straight positive months, the S&P 500 was up over the next 12 months 70% of the time. That’s really not a terribly high success rate. The average return is only about 7%, and the median is even lower than that. The wide range of returns over those previous 20 instances doesn’t really make the case for predictability either.

Expand

SNPINDEX: ^GSPC

S&P 500 Index

Today’s Change

(-0.43%) $-29.98

Current Price

$6878.88

Key Data Points

Day’s Range

$6831.74 - $6882.96

52wk Range

$4835.04 - $7002.28

Volume

4.6B

To put those numbers into some context, here are the subsequent 12-month returns for all months going back nearly 100 years for the S&P 500 (~100 years * 12 months/year = roughly 1,200 data points).

Essentially, this is what you could expect on average by investing in the S&P 500 for a 12-month period.

Data source: Yahoo! Finance.

Regardless of how the index performs in any given month, it’s up 12 months later 69% of the time, almost the exact same success rate as when it’s coming off a seven-month winning streak. The returns, however, look much different. The average 12-month forward return is about 8%, but the median is nearly 10%.

I don’t want to overstate the importance of a sample size of 20, but there does seem to be a meaningful difference in what forward-looking returns are, historically speaking. The median 12-month forward return in all months is about 10%, but it’s only just over half of that when coming off a seven-month streak of positive returns.

In short, history says to expect returns over the next 12 months that are below the S&P 500’s long-term average. After a lengthy winning streak, such as the one that just wrapped up, a period of underperformance appears likely.