Apple and Nvidia have become two of the main forces driving the broader U.S. stock market. According to Sina Finance, Creative Planning President Peter Mallouk said the S&P 500's concentration in the two stocks is unprecedented, with Apple and Nvidia together accounting for more than 15% of the index.

That share is above the 9.1% combined weight of Microsoft and General Electric before the dot-com bubble burst. Apple shares touched $345 on Tuesday, a record high for the iPhone maker, before easing slightly from that peak as the broader market pulled back. Earlier this month, Apple launched the iPhone 18 and its first foldable phone, Duo, after which the stock began a strong rally and is up 25% this year. Nvidia said in late August that revenue growth in its next fiscal year could reach at least 70%, and Chief Executive Jensen Huang said growth would exceed 100% if supply bottlenecks did not constrain the company. Nvidia shares are up 21% this year.