It is important to remember that future rates of return can't be predicted with certainty and that investments that pay higher rates of return are generally subject to higher risk and volatility. The actual rate of return on investments can vary widely over time, especially for long-term investments. This includes the potential loss of principal on your investment. It is not possible to invest directly in an index and the compounded rate of return noted above does not reflect sales charges and other fees that funds and/or investment companies may charge.
When you are taking periodic distributions from an account or investment, the return earned is often lower due to more conservative investment choices to help insure a steady flow of income.