S&P 500 Market-Cap Weighting: Energy Outperforms, AI Still Drives the Index

In 2026, the energy sector in the US S&P 500 index posted a year-to-date gain of nearly 55%, far exceeding technology's 29.6%, yet the index itself remains primarily driven by technology (including AI). James Picerno of The Capital Spectator notes that this apparent paradox stems from market-cap weighting: technology carries a weight of nearly 39% in the S&P 500 while energy accounts for only 3.8%, so even though energy's return is larger, its actual contribution to total index return falls far short of technology's.

Picerno illustrates this structure with two exclusion ETFs. SPXE, which removes energy, returned 12.0% year to date versus 13.3% for the standard S&P 500 ETF (SPY)—a gap of just 1.3 percentage points. By contrast, SPXT, which removes technology, performed markedly worse than the benchmark. This means energy's powerful rally is diluted at the index level by its small weight, and technology's structural dominance is not shaken by short-term underperformance.

The author's core judgment is: as long as investors remain confident that AI can drive faster revenue growth, wider profit margins, and new business opportunities, technology stocks are likely to remain the cornerstone of the bull market. But he also raises an observable boundary condition—data from John Butters at FactSet shows that the Magnificent 7 have reported higher year-over-year earnings growth than the other 493 S&P 500 companies over the past several quarters; FactSet projects that for Q4 2026, the Magnificent 7's growth rate (23.6%) will fall below that of the remaining 493 (30.6%) for the first time since Q4 2022. If this projection materializes, at least in relative terms, the signal that AI's earnings advantage is peaking becomes concretely testable.