Long a Wall Street favorite, Nvidia has not outperformed the broader market recently, falling 3% over the last six months, worse than the S&P 500’s 7% return.

What happens with Nvidia matters for the entire U.S. stock market. The chip company has grown into the second-largest company on Wall Street, which means the stock’s movement carries more weight on the S&P 500 and other indexes than every company except Apple. The tech giant, based in Santa Clara, California, is now worth over $3 trillion.

Legendary value-stock investor Bill Nygren, co-manager of the Oakmark Fund OAKMX, says that the S&P 500 “looks more like a growth fund today than it ever has” — but he adds that the benchmark U.S. stock index isn’t overpriced.