Stocks had an ostensibly great day. But something alarming happened, not seen since 1999.

Monday was by all accounts a great day for the stock market. of Nasdaq Composite It rose 2%, setting a new record. broader S&P500 It rose about 1.5% and is now less than 1% below its new high.

But traders are talking about something unhealthy going on behind the scenes.

On Monday, more stocks in the index fell to 52-week lows than rose to 52-week highs. Specifically, 30 stocks in the S&P 500 made new lows, while only seven made new highs.

The last time a new low exceeded a new high and the index rose at least 1% to within at least 1% of a new 52-week high was on December 21, 1999, several months before the peak of the dot-com bubble. Jason Goepfert, founder of SentimenTrader and current advisor to NextGen News.

Previously, the only time in history such a dynamic had unfolded was on July 23, 1929, he said in a post to X.

When it comes to Monday’s trading action, it’s all about where exactly the leadership comes from, said Art Hogan, chief market strategist at B. Riley Wealth.

The S&P 500’s gains were led by communications services, information technology, and consumer staples, with information technology remaining less than 1% from its 52-week high, while communications services and consumer finance have retreated further, at 4% and 7% below their respective highs.

“Management teams are battling near-term performance weakness, and what’s sold continues to be sold, so it’s easier for today’s management to create new lows than to create new highs,” he said.

Hogan added that the market could see sporadic trading days like this in the coming months if sentiment remains subdued amid tensions in the Middle East.

“If the war drags on, energy prices stay high, and the Fed has to keep raising rates, we’re not going to see new all-time highs in this market,” he said.

The S&P 500 rose more than 13% in 2026. It’s also up more than 19% in the past six months.

—CNBC’s Christopher Hayes contributed to this report.