The S&P 500 keeps climbing on days when stocks broadly struggle. Here’s what’s going on.

A small number of large-cap technology stocks with significant market values have generated outsized influence over S&P 500 daily performance. These stocks have accounted for a substantial portion of the index's gains on days when broader market participation has been limited. The concentration of gains in a narrow group of stocks means the index can rise even as most individual stocks decline.

Next story