We investigate how the S&P committee balances the Index’s goals of representing the U.S. equity market as well as capturing the performance of the equity market through its addition/deletion decisions. Our results show that the Index represents the US equity market very well by maintaining large stocks. However, these large stocks underperform the Index by 0.24% per month. The index committee makes up the lower performance of these stocks by adding high-performance stocks when deletions occur. The deletion/addition events are therefore crucial in both representing the equity market and tracking it performance.