S&P 500 rally masks broad weakness as AI heavyweights drive 2026 gains

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S&P 500 AI-driven rally

Highlights

The median S&P 500 stock is up just 4% in 2026, while more than 200 constituents are negative and a quarter have dropped at least 11%.
S&P 500 technology sector gained 32% and energy 42% in 2026, but technology alone drove over 10 percentage points of the index’s advance.
Nvidia, Apple, Micron, and Advanced Micro Devices together contributed over 5% to the S&P 500’s rise as higher yields pressure non-AI sectors.

Market breadth weakens beneath index highs

As reported by Reuters, an analysis of LSEG data shows the median S&P 500 stock is up barely 4% in 2026, far below the benchmark's overall advance as gains cluster in a few chipmakers and other large technology names.

The analysis covers current S&P 500 members and excludes 18 companies removed from the index in 2026, including some that were shifted to smaller-capitalization indexes after stock declines. More than 200 companies in the index are lower this year, and about a quarter of constituents are down 11% or more.

The gap between the benchmark and its average member underscores how much of Wall Street's rally depends on a handful of companies as the U.S. bull market nears its four-year anniversary. Memory-chip makers Sandisk and Micron Technology have more than tripled, while fewer than half of current S&P 500 companies are trading above their 200-day moving averages, a sign of limited strength across the broader market.

AI leadership and rate risks shape investor outlook

Technology and energy are leading sector gains in 2026, with the S&P 500's technology sector up 32% and energy up 42%. Because of its much larger weight in the index, however, technology accounts for more than 10 percentage points of the benchmark's gain, while energy contributes less than 1%.

Nvidia has contributed nearly 2% to the S&P 500's rise this year, followed by gains of more than 1% each from Apple, Micron and Advanced Micro Devices. Recent earnings growth from AI-linked companies continues to support the broader index even as profit expansion in many other sectors remains muted.

Strategists and investors say higher yields and the prospect of further Federal Reserve tightening remain a challenge for stocks outside the AI theme. Ross Mayfield, investment strategy analyst at Baird, says companies beyond AI and energy face significant headwinds, while Tim Ghriskey, senior portfolio strategist at Ingalls & Snyder, says the AI trade is attracting managers and assets so strongly that many other stocks are being overlooked.

Our earlier coverage of AI investment and its economic spillovers examined whether the AI-led stock rally is translating into wider U.S. economic concentration. We noted that while AI-related data center and infrastructure spending is contributing to growth, the bigger macro channel may be the wealth effect from rising equity values—meaning a reversal in AI-driven gains could ripple into consumer spending and broader activity.

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