The S&P 500 index is approaching its all-time closing high, a rally primarily fueled by the outsized gains of Nvidia, Apple, and Microsoft. These three tech giants have grown so large that their strength alone can pull the entire index higher, even as the broader market experiences weakness. Since mid-August, only two of the S&P 500's 11 sectors—technology and energy—have gained ground. The real estate sector has been the worst performer, pressured by surging interest rates.