The S&P 500 is considered the primary benchmark for the broader stock market.Composed of roughly 500 of the most well-known large-cap U.S. stocks, the S&P 500 index is a benchmark for the entire market, which is why so many investors choose to own the index in one way or another. Over many decades, it can be very difficult for investors to outperform the broader market with their own investing strategies.And over the past five years, the S&P 500 has seen particularly strong returns, nearly doubling in that ...