The S&P 500 index is a benchmark of American stock market performance, dating back to the 1920s. The index has returned a historic annualized average return of around 10% since its inception Here are the average mutual fund returns for seven major categories used by Morningstar, Inc. The figures represent the average for all mutual funds, including index funds, within the respective category. The 3-,5-,10-, and 15-year figures represent the average annual return over given time periods. However, investors should also look at a fund's yearly performance to fully appreciate the consistency of its annual total returns. For example, a five-year average annual return of 10% looks attractive; however, if the yearly returns (those that produced the average annual return) were +40%, +30%, -10%,