Key Highlights

● Eight of 11 S&P 500 sectors rose while the index fell 23.59 points to 7,720.39.

● Alphabet's worst day since its 2004 IPO erased roughly $500 billion in market value.

● NYSE advancers beat decliners by 1.95 to 1, with 19 new 52-week highs.

● Cap-weighting let a handful of technology giants outweigh gains across hundreds of members.

Most of the market went up on Thursday, but the S&P 500 still closed lower, a lopsided result explained by the outsized weight of a handful of technology giants.

The paradox in numbers

Here is the puzzle. On Thursday, October 29, eight of the 11 S&P 500 sectors finished higher and more than 400 of the index's members rose, according to market data. Another count put advancers at 406. Yet the benchmark itself slipped 23.59 points to 7,720.39, ending a three-day winning streak.

Another source confirmed the sector count, noting that health care and utilities were among the gainers. Only three sectors fell: communication services, information technology and consumer discretionary.

How three sectors outweighed eight

The answer lies in how the S&P 500 is built. It is weighted by market value, so the largest companies have the biggest influence. A sharp fall in one giant can outweigh modest gains in hundreds of smaller members.

Thursday delivered exactly that. Alphabet (NASDAQ:GOOGL) suffered its worst day since its 2004 IPO, erasing roughly $500 billion in market value, according to media reports. One report described it as the second-largest one-day wipeout on record, after Nvidia (NASDAQ:NVDA)'s $589 billion loss in January 2025. Alphabet's slide was almost entirely responsible for communication services finishing as the worst sector by a wide margin.

Technology fell as ServiceNow (NYSE:NOW), Fortinet (NASDAQ:FTNT) and Marvell Technology (NASDAQ:MRVL) tumbled. Consumer discretionary slid because Amazon (NASDAQ:AMZN), its largest member, fell to $243.79 before its after-hours report.

The eight that rose

Health care led, powered by Eli Lilly (NYSE:LLY)'s all-time closing high of $1,373.70 and Merck (NYSE:MRK)'s beat and raised outlook. Real estate came second, helped by a dip in Treasury yields. Consumer staples and utilities followed closely, as investors sought steadier earnings. Financials and industrials also gained, with Mastercard (NYSE:MA), Huntington Ingalls (NYSE:HII) and Textron (NYSE:TXT) among the standouts.

Energy was one of the closest calls. A midday market snapshot showed energy funds slightly lower as oil prices eased, with West Texas Intermediate settling at $102.00 a barrel, down 78 cents, according to media reports.

What breadth says about the market

The internals told a healthier story than the headline. NYSE advancers beat decliners by 1.95 to 1, according to media reports, while Nasdaq advancers edged out decliners by 1.07 to 1. The S&P 500 logged 19 new 52-week highs and only 6 new lows. Volume reached 17.05 billion shares, almost exactly in line with the 20-day average of 17.09 billion, a sign of orderly trading rather than panic.

The small-cap Russell 2000 climbed 28.71 points to 2,859.22. One source said the equal-weighted S&P 500 rose, though its own price data suggested the fund was roughly flat, so sources differed.

One market strategist said: "Money is rotating within the market rather than leaving it." Another strategist pointed to the small-cap outperformance as a constructive sign for how the market was reading the day.

The concentration question

Days like Thursday highlight how dependent the cap-weighted S&P 500 has become on a handful of companies. When those giants rally, they mask weakness elsewhere. When they fall, as Alphabet did, they can turn a broad advance into an index decline.

The Nasdaq Composite, more heavily weighted toward technology, felt it most, dropping 365.13 points to 26,184.72. The Dow, which does not include Alphabet, lost a more modest 132.54 points to 52,342.56.

What to watch

The next test arrives Friday. Amazon and Intel (NASDAQ:INTC) fell sharply in extended trading on Thursday, and Nasdaq-100 futures slid after the bell, according to market data. That sets up another session in which a few large names could again outweigh the rest. Friday's Employment Cost Index, plus Earnings from Chevron (NYSE:CVX) and AbbVie (NYSE:ABBV), will show whether broad participation can keep holding up.