If you’ve glanced at your investment portfolio lately and noticed the market indexes ticking upward, you might assume the whole stock market is doing well. The reality is a bit more complicated — and worth understanding.
This year’s rally in the S&P 500 is largely the work of a surprisingly small group of companies. The top 10 stocks have contributed 5.1 percentage points to the S&P 500’s return in 2026, and the top 20 stocks have contributed 6.5 percentage points — actually exceeding the index’s overall 5.7% return, because many other stocks are dragging it down and offsetting the winners. ETF.com
In other words, the index looks healthier than it actually is.
The AI Infrastructure Story
The stock market rally is broader than it was in 2024 and 2025, but it is almost entirely an AI infrastructure story. ETF.com
The biggest winners this year are companies building or supplying the technology that powers artificial intelligence. Alphabet sits near the top of the list, with Broadcom close behind as Alphabet’s design partner on custom AI chips and a collaborator with OpenAI and Meta as well. Amazon comes in third, with AWS cloud demand accelerating and its custom chip program gaining traction. Nvidia ranks fourth, still a significant market driver — though it no longer dominates the way it did in previous years. ETF.com
One of the more surprising stories belongs to Intel. Intel has averaged just 0.39% of the index but has contributed a disproportionate share of returns. The stock more than doubled in April alone and is up 156% on the year, driven by surging CPU demand from AI workloads and growing confidence that Intel’s foundry business might actually turn around. ETF.com
The Rotation Away from Big Tech
Not every chapter of this story is about AI chips and cloud computing. A broader market rotation is also underway, with industrial, consumer defensive, and energy stocks leading the market higher as some technology names falter and investors look beyond the AI trade for returns. Morningstar
Caterpillar has been one of the standout performers, up 32% this year and responsible for a significant share of the industrial sector’s gains. Analysts note that investors have come to see Caterpillar as a beneficiary of the AI infrastructure buildout, since data centers require enormous amounts of construction equipment and power infrastructure. Morningstar
On the consumer side, Walmart and Costco have had the largest impact in their sector. As consumer spending slows and households shift toward more economical options, investors have moved into these defensive names. Walmart’s strong return this year accounts for more than two percentage points of its sector’s overall gain. Morningstar
In energy, oil giants Exxon Mobil and Chevron have had the biggest impact, with energy stocks up more than 22% since the start of the year. Chevron has returned over 21% and accounts for a notable share of the sector’s total return. Morningstar
The Part That Should Give You Pause
The US stock market’s rally to new highs has been propelled by so few stocks that it’s reminding some on Wall Street of the runup to the dot-com bubble. While the comparison has limits — today’s leading companies are generating massive real profits, unlike many dot-com era names — narrow market breadth is still raising concern among investors and analysts. Bloomberg
Some of the biggest names in the market are actually working against the index. Microsoft has been the single biggest drag, shaving nearly a full percentage point off returns on its own. Investors are growing worried that AI could end up disrupting Microsoft’s core software business even as the company invests heavily in it. Tesla, Eli Lilly, Meta, and Palantir are also among the notable detractors from the index’s return this year. ETF.com
What This Means for Everyday Investors
When you own a broad index fund, you own a little bit of everything — the winners and the losers. Right now, the winners are doing enough to pull the whole thing forward, but the foundation is narrower than the headline numbers suggest.
That isn’t necessarily a reason to panic. Markets have rallied on narrow leadership before and gone on to broaden out. But it is a good reminder that a rising index doesn’t mean every company inside it is thriving — and understanding what’s actually driving the numbers is always worth your attention.
This article is for informational purposes only and does not constitute financial advice.
