If you invested $100 in the S&P 500 at the beginning of 1998, you would have about $715.90 at the beginning of 2021, assuming you reinvested all dividends. This is a return on investment of 615.90%, or **8.67% per year**.

This investment result beats inflation during this period for an inflation-adjusted return of about 326.56% cumulatively, or **6.32% per year**.

The graph below shows the performance of $100 over time if invested in an S&P 500 index fund. The returns assume that all dividends are automatically reinvested.

This chart shows the rate of gains and loss by month, including dividends:

The *nominal* return on investment of $100 is $615.90, or 615.90%. This means by 2021 you would have $715.90 in your pocket.

However, it's important to take into account the effect of inflation when considering an investment and especially a long-term investment. You can convert S&P returns to their *real* (inflation-adjusted) value using an inflation calculation based on the U.S. Bureau of Labor Statistics Consumer Price Index (CPI).

In the case of the returns described above, the CPI in 1998 was 163.000 and the CPI in 2021 was 273.567.

The ratio between these CPIs describes how relative buying power of a dollar has changed over 23 years.

Adjusted for inflation, the $715.90 *nominal* end value of the original $100 investment would have a *real* value of roughly **$326.56** in 1998 dollars. This means the inflation-adjusted return is **326.56%** as opposed to the original 615.90%.

For more information on inflation, see our U.S. inflation calculator for 1998.

The table below shows the full dataset pertaining to a $100 investment, including gains and losses over the 284-month period between 1998 and 2021.

Note that data shown is the *monthly average closing price*. Returns include dividends.

The information on this page is derived from Robert Shiller's book, Irrational Exuberance and the accompanying dataset, as well as the U.S. Bureau of Labor Statistics' monthly CPI logs.

Note that S&P index value for the current quarter is based on a moving average of closing prices, per Robert Shiller's methodology. The inflation data used is based on annual CPI averages.

Start Value
Average monthly close |
$963.36 |

End Value
Average monthly close |
$3,278.20 |

Change in price |
+240.29%
+5.72% / yr |

Change incl. dividends |
+615.90%
+8.67% / yr |

Change, inflation-adjusted |
+326.56%
+6.32% |

Final amount, nominal ($100 base) |
$715.90 |

Final amount, inflation-adjusted ($100 base) |
$426.56 |