Just over half of U.S. stocks rose Monday. Meta and the chipmakers still moved the S&P 500
On Monday, September 21, 2026, 3,019 of 5,851 U.S. common stocks advanced; SPY gained 1.55% while equal-weight RSP gained 0.18%.
Meta Platforms, Intel and Advanced Micro Devices jumped with Nvidia, already 8.1% of the S&P 500 fund SPY and up 2.3% Monday. Those four holdings contributed 0.68 percentage points of the fund’s 1.55% gain at Monday’s close. Barron's reported Monday that Meta's Muse AI agent was the trigger for the chip rally, with Intel, AMD and Arm Holdings moving together.
Arm, Intel, Meta and AMD jumped far past the S&P 500
- +17%
- +12%
- +11%
- +9.9%
That is not a market in which the typical stock set the pace. It is a market in which the typical stock was present.
Half the board advanced. Cap-weight still led
Among 5,851 U.S. common stocks listed on the NYSE, Nasdaq and NYSE American, 3,019 finished higher, 2,604 finished lower, and 228 were unchanged. Just over half the board advanced. That is the opposite of Friday, when the Nasdaq-100 fund rose 0.63% as 3,418 U.S. stocks fell. It is closer to Thursday, when 3,480 stocks rose and the S&P 500 still needed chips.
A majority of names can rise and the cap-weighted index can still be a different session. The equal-weight S&P 500 fund RSP rose 0.18% on share price, 1.37 percentage points behind SPY. RSP went ex-dividend $0.80 a share on Monday. A dividend is not a rally.
On the same share-price basis, the Nasdaq-100 fund QQQ, which also went ex-dividend Monday, rose 2.77%. The Russell 2000 fund IWM rose 0.51%, a 2.26-percentage-point gap.
Seventeen of 20 mega-cap stocks rose. The three that did not were Berkshire Hathaway Class B, down 1.5%, Exxon Mobil, down 3.1%, and Johnson & Johnson, down 0.2%. Apple, the second-largest holding in SPY, rose 0.8%; Microsoft rose 1.6%.
The 10 largest holdings are 38.6% of SPY. That concentration is the mechanism. Meta is 2.2% of the fund and contributed 0.25 percentage points by itself. Intel is 0.8% of the fund and still added 0.10 percentage points. Equal-weight cannot do that: Meta is about 0.2% of RSP.
The past month already had this shape
Monday did not invent the split.
Equal-weight has lost 3.1% over the past month; SPY has not
- +1.7%
- −3.1%
Joe Mazzola, head trading and derivatives strategist at Charles Schwab, noted Monday morning that last week ended with only around 30% of S&P 500 stocks above their 50-day moving average.
Small-caps have not lost 2026.
Small-caps lead 2026. Equal-weight large-caps trail
- 17%
- 14%
- 12%
The divide is not big versus small. It is a handful of AI-adjacent names against everything else, most large caps included. Monday’s gap did not land on small-caps. It landed on holders of the equal-weight S&P 500.
Frequently asked
Why did SPY gain so much more than the equal-weight fund?
Four holdings, Meta, Intel, AMD and Nvidia, contributed 0.68 of SPY's 1.55 percentage-point gain, and those stocks carry far bigger weights in the cap-weighted fund than in equal-weight.
Did most stocks actually fall on Monday?
No: 3,019 of 5,851 U.S. common stocks advanced, so just over half the board rose.
What set off the chip rally?
Barron's reported that Meta's Muse AI agent was the trigger, with Intel, AMD and Arm Holdings moving together.
Are small-caps the ones being left behind?
No: the Russell 2000 fund leads 2026 with a 16.8% total return, ahead of both SPY and the equal-weight fund.