David Moadel
5 min read
Quick Read
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The S&P 500 gained 17% over 8 weeks, ranking as the 20th biggest 8-week advance since January of 1950.
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Reportedly, similar rallies have averaged 10% gains over the following 3 months, 14% over 6 months, and 27% over 12 months—all materially higher than baseline periods.
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Investor expectations for mean reversion after sharp rallies have often been wrong, as momentum in the S&P 500 tends to compound rather than reverse at this magnitude of move.
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Although the S&P 500 has gained 17% over the past 8 weeks, the instinctive reaction across Wall Street has been familiar: brace for a pullback. Yet, the historical record, as compiled by research firm Creative Planning, points in a direction most market watchers would not guess.
According to a Creative Planning analysis posted by Daily Chartbook on X, the 8-week run that just unfolded for the S&P 500 ranks as the 20th biggest 8-week gain for the index since 1950. That is rarefied air across more than seven decades of trading history. However, what tends to follow stretches like this isn’t the snapback that you might expect.
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This piece walks through Creative Planning’s forward-return averages and what they suggest about the asymmetry between investor expectations and historical outcomes. The numbers tell a different story than the typical bearish forecast.
An 8-Week Sprint That Lands in the History Books
The benchmark S&P 500, tracked by many retail investors through the SPDR S&P 500 ETF Trust (NYSEARCA:SPY), just posted a 17% gain over the past 8 weeks. Creative Planning’s data set spans January 1950 through May 2026 and ranks this stretch as the 20th out of every rolling 8-week window in that span.
Most investors carry an instinctive expectation that markets revert. After a sharp move higher, the natural assumption is that the trend has borrowed from future returns, leaving the index vulnerable to digesting its gains.
The result is uncomfortable for the mean-reversion camp. Stretches like this one have historically been continuation events more often than exhaustion events for the S&P 500.
What Has Historically Followed Rallies This Big
Creative Planning’s analysis isolates every prior instance of an 8-week rally of this magnitude and tracks the S&P 500 forward across three windows. The pattern is consistent across all three.
