Ben Snider of Goldman Sachs warns that a small number of stocks are driving the U.S. equity market to new highs.

This concentration of gains suggests that the broader rally may lack a sustainable foundation, potentially increasing the risk of a market correction if the leading stocks falter.

Snider, who serves as the chief U.S. equity strategist and managing director at Goldman Sachs Group Inc., identified "yellow flags" for equities during a Tuesday interview. He said that while the S&P 500 index has reached an all-time high, the internal health of the index is uneven.

According to Snider, the median stock in the S&P 500 is currently about 13% [1] below its own respective high. This gap indicates that the majority of companies in the index are not participating in the current peak performance.

"If you look at the S&P 500, we’re at an all-time high, but the median stock in the index is still about 13% below its respective high," Snider said.

He said that limited market breadth is a primary concern. Because gains are concentrated in a few specific stocks, the broader market performance remains vulnerable to the volatility of those few leaders.

Snider said the current trend shows that the market is not broadening out in a way that supports long-term stability. The disparity between the index peak and the median stock's performance serves as a warning sign for investors regarding the quality of the current rally.

the median stock in the index is still about 13% below its respective high

Market breadth is a key indicator of a healthy bull market; when a wide variety of stocks rise together, the trend is generally more sustainable. By highlighting that the median stock is lagging significantly behind the index high, Snider is suggesting that the S&P 500's record levels are being skewed by a few outliers rather than broad economic growth across the index's components.