The Market Has Never Been This Crowded. Last Thursday Showed What That Costs.

Last Thursday the Nasdaq fell 2.6%, its steepest one-day drop since early June. The Philadelphia semiconductor index lost 6.7%. Meta fell 7% after reporting its first cash outflow in more than a decade, the cost of its AI buildout. And the Dow finished the day up.¹

That split is the story of this market. Paul Nolte of Murphy & Sylvest told Reuters that technology, “which has been the golden child of the markets up until about June,” was the only part of the market really suffering, and that the indexes are so heavily weighted toward it that the tech selloff pulled them down too. “Investors are starting to realize that there are some holes in the AI story,” he said.¹

Three stocks, one fifth of the index

Earlier this month, on October 6, the S&P 500 closed at a record 7,818.93. That same day Nvidia, Apple and Microsoft together made up more than 21% of the index, the highest three-stock concentration in its history. The previous record was set in the mid-1980s, when IBM, AT&T and ExxonMobil peaked at a combined 13.4%.²

Widen the lens and it gets starker. The ten largest stocks are about 40% of the S&P 500, and technology plus communication services is about half of it.³ For most of the 1990s the top ten held 18% to 19% of the index. At the 2000 peak they reached 26%. In 2020 it was 27%, in late 2024 it was 34%, and now it is above 40%. Those ten companies are projected to produce about 32% of the index’s earnings, so their weight runs well ahead of their profits.⁴

The index is up. Most stocks are not.

Here is the part the headline number hides. On the day the S&P 500 set its record, only about a quarter of its stocks were trading above their 50-day moving average. On August 13, the previous record day, about 68% were. Since early August only technology and energy have beaten the index, and seven sectors are negative.³

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The equal-weight version of the S&P 500, which gives every company the same vote, tells the same story. Its ratio to the cap-weighted index sits just above the lowest reading since the equal-weight fund launched in 2003, a low set on May 15 of this year. Over the past year equal weight has trailed by 3.8%.⁵

“Every index on the planet is basically an AI index,” Matt Miskin of Manulife John Hancock Investments said on Yahoo Finance on Thursday.⁶ If you own the S&P 500, you own a bet on a few companies whether you meant to or not.

The crowded names are moving

Those few companies are not sitting still. Nvidia closed Thursday at $212.21, down 4.4% on the day, on volume about 19% above its 30-day average. At a $5.11 trillion market value it is 12.8% below its 52-week high of $243.37.⁷ That high was set on October 6, the same day the index peaked.²

SpaceX, the other name every retail investor seems to be watching, has been a roller coaster since its June listing at $135.⁸ It traded at $185 on June 18 and $123.54 by July 21, a 33% drop in a month.⁹ It closed at $108 on August 5 after its first earnings report, then climbed about 50% to around $163 by October 12. Its largest insider unlock, up to 1.3 billion shares, was scheduled for the second full trading day after its third-quarter results.⁸ Those results landed on October 20: revenue of $14.6 billion and the company’s first profitable quarter since going public.¹⁰

Two dates on the calendar

The Federal Reserve wraps up its meeting tomorrow, Wednesday, with a decision at 2 p.m. Eastern. Its target range is 3.75% to 4% after a quarter-point hike in September. Futures put the odds of a hold at about 90%, and traders broadly expect a hike at the December 8-9 meeting.¹¹ On Thursday the market was already pricing in the odds of a quarter-point increase before year-end, while crude hit a five-month high after Houthi strikes on Saudi targets.¹

Then comes next Tuesday, November 3, Election Day. All 435 House seats and about a third of the Senate are on the ballot.¹² Whatever the result, the makeup of Congress for the next two years will be settled within hours, and markets will reprice tax, spending and tariff expectations around it.

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The warnings are not coming from cranks

On October 13 the International Monetary Fund’s Global Financial Stability Report flagged investor concentration in a few technology firms, circular financing among AI companies and rising government bond yields as risks, while stopping short of predicting a collapse.¹³ On IBM’s earnings call last week, chief executive Arvind Krishna said clients “are also getting worried if some of the AI spending is completely out of control with no real return.”⁶

Not sell everything. Own what matters.

It would be easy to read all this as a reason to get out. That is the wrong lesson. The S&P 500 is still up 11.9% this year and the semiconductor index is up 51.5%, even after Thursday. Of the 111 S&P 500 companies that had reported third-quarter results, 83% beat estimates. And on the day tech fell, Blackstone rose 8.4%, Lockheed Martin 7% and Procter & Gamble 5.6%.¹ Money did not leave the market. It moved.

Money did not leave the market. It moved.

The lesson is about selection. When ten names are 40% of the index and three are more than a fifth, buying the index is buying those names. When three quarters of the index is below its 50-day average, most of the other stocks are not participating. The gap between the few that are working and the many that are not has rarely been this wide, and that gap is likely where the next year’s returns get decided.

The risk runs the other way too. Concentration was called a danger at 26%, at 34% and at 40%, and the index kept climbing. A Fed hold tomorrow and a clean election next week could send the crowded names straight back to their highs. Chasing a rotation that never comes has cost investors before, and nobody can say with confidence which day the pattern changes.

But the question investors should be asking this week is not whether to own stocks. It is which ones. The crowded trade is crowded because everyone can see it. The harder work is finding the handful of companies that earn their place in a portfolio on their own numbers, not on their index weight, before the Fed, the election and the next earnings report force the issue.