Why the Stock Market Can Go Up When Most Stocks Go Down
On September 21, 2026, the Dow Jones Industrial Average rose 0.71% to 52,048.83 points while the Nasdaq rose 2.26%.
Nasdaq data for that day showed 64 new highs and 127 new lows, according to Reuters. Breadth means how many stocks rose versus how many fell. Breadth was negative. New lows were about twice new highs even though the index rose more than 2%.
A September 22 report noted the same split in the wider market. New 52-week lows had recently outnumbered new 52-week highs while the S&P 500 sat near record levels, according to Yahoo Finance. It pointed to CoStar Group, down 56.1% in 2026 at the time, while the benchmark stayed near highs.
The S&P 500 last closed at a record high on August 13, 2026. As of September 10 reporting, it was down nearly 3% from that close but still up 11% in 2026, according to Reuters.
As of September 9 reporting, stocks stayed near record highs despite recent swings in the bond market. Measures of volatility were near 2026 lows, according to Reuters. Volatility means how much prices jump around.
Concentration has been part of the discussion for months. MarketWatch hosts an article on investing in a highly concentrated stock market at the URL ending afec4d5e, published May 13, 2026. In that coverage, Jed Ellerbroek is identified as a portfolio manager at Argent.
The broader context here is that the main indexes are averages where the biggest companies count the most, like a class average pulled up by a few top test scores. When new lows grow while the S&P 500 stays near highs, a smaller group is holding up the average. A fall the size of CoStar's can happen with a double-digit index gain for the year if big-company weight offsets weakness elsewhere. Calm volatility next to high levels left little cushion for shocks from the economy or interest rates. For risk checks, the key items are active share versus the benchmark, factor exposure to momentum and size, and the new high-new low gap as a confirmation sign.
Looking at what this means for everyday portfolios, crowding and liquidity matter more now. Crowding means many investors in the same stocks. Liquidity means how easily you can trade. Narrow breadth widens tracking error, the gap between a mixed portfolio and the index, and raises sensitivity to rotation, when money shifts fast from one group to another. Low volatility lowers the cost of hedging with options, but also lowers the payoff for holding exposure into risky events. September leaves open both paths, with breadth possibly confirming the index or the index moving toward breadth.
