The S&P 500 Momentum Index, which tracks stocks with the strongest recent price trends, has ripped 32% higher over two months. That’s the best performance in the index’s history, and it’s not particularly close.
April alone accounted for a 19.3% return, making it the single strongest month on record for the momentum gauge. The move was fueled almost entirely by mega-cap AI stocks dragging the rest of the market upward.
The numbers behind the rally
The Nasdaq Composite surged 25% during April and May 2026, its best two-month stretch since late 2002. For context, the last time the Nasdaq moved that aggressively over two months, the market was recovering from the dot-com crash.
The S&P 500 itself added over $9.5 trillion in market capitalization in recent weeks. It hit 14 record highs in a single month. That kind of concentrated buying pressure, largely channeled through AI-related names, created ideal conditions for momentum strategies to compound on themselves.
Goldman Sachs’ own Momentum Factor climbed 25% over three months, which the bank flagged as a historic rally by any measure. Hedge fund exposure to momentum trades is now approaching five-year highs.
On the global stage, the MSCI global momentum index outperformed the MSCI All Country World Index by 17 percentage points since March 2026. According to Goldman Sachs and S&P Global data, that’s the widest gap since 1991.
Why history suggests caution
Goldman Sachs examined historical patterns of momentum bursts that coincided with the S&P 500 trading near all-time highs. The finding was sobering: these sharp surges are typically followed by short-lived peaks. Median forward returns over the next one to three months have historically been close to zero.
Goldman Sachs’ data on hedge fund positioning is particularly worth watching. With momentum exposure near five-year highs, there’s a crowding risk that doesn’t show up in standard volatility metrics.
For crypto-adjacent investors, the dynamic matters because risk appetite in traditional markets directly influences capital flows into digital assets. The correlation between crypto and tech-heavy indices tends to spike during exactly these kinds of regime changes.
The smartest move might be the least exciting one: acknowledging that a 32% two-month gain is, by definition, an outlier event, and sizing positions accordingly. When a strategy posts its best return in recorded history, the base rate for repeating that performance is essentially zero.