Stocks had a great day on the surface. But something alarming occurred not seen since 1999

The stock market just posted a banner day by nearly any measure on Monday. The Nasdaq Composite surged 2% to a new record. The broader S&P 500 jumped about 1.5% and now sits less than 1% below a new high. But traders are buzzing about something unhealthy that occurred under the surface. More stocks fell to new 52-week lows on Monday than rose to 52-week highs in the index. More specifically, 30 S&P 500 stocks hit new lows, while only seven reached fresh highs. The last time the index advanced at least 1% to within 1% of a new 52-week high as new lows outnumbered new highs was Dec. 21, 1999, a few months before the Dotcom Bubble top. That's according to Jason Goepfert, who founded SentimenTrader and now serves as an adviser at NextGen News. Prior to that, the only other time in history this dynamic has played out was July 23, 1929, he noted in a post on X. For Monday's trading action, it all comes to where the leadership is coming from exactly, according to Art Hogan, chief market strategist at B. Riley Wealth. The S&P 500's gains were led by communication services, information technology and consumer discretionary, and while information technology stands less than 1% from a fresh 52-week high, communication services and consumer discretionary sit much farther back at 4% and 7% below their respective highs. "The leadership's battling against weaker performance in the near term, and what's selling off has been selling off, so the creation of new lows has an easier glide path than the creation of new highs with today's leadership," he said. Hogan added that the market could experience more trading days like this sporadically over the coming months if sentiment remains subdued amid tensions in the Middle East. "We're not going to make new highs in this market if the war persists, energy prices remain stubbornly high and the Fed has to continue to hike rates," he said. The S&P 500 has risen more than 13% in 2026. It's also gained more than 19% in the last six months. — CNBC's Christopher Hayes contributed to this report.