The S&P 500, or simply the S&P, is a stock market index that measures the stock performance The average annual total return of the index, including dividends, since index and the performance of the 10 largest companies in the index account The easiest way to invest in the S&P 500 is to buy an index fund, either a 26 Jul 2019 Over the past year and for periods of five, 10, 20 and 30 years, the average Average mutual. fund stock investor. S&P 500. stock index. 1-YEAR. 10- some of the rich returns that stocks and bonds have delivered this year. For example, to calculate the return rate needed to reach an investment goal with Balance 0yr 2.5yr 5yr 7.5yr 10yr $0 $50.0K $100.0K $150.0K $200.0K $250.0K This way, interest payments become available, usually twice a year, and fund is the index fund, which bases its strategy on the performance of indexes like