The withdrawal rate refers to the percentage or amount of money that is withdrawn from a retirement account, such as an IRA or 401(k), on an annual basis. This can be used as a guide for determining how much income one may have in retirement and how long their savings may last. The withdrawal rate is typically based on assumptions about the investment performance of the portfolio, inflation rates, and life expectancy. It's important to note that if the withdrawal rate exceeds the account balance, it could deplete the funds prematurely. Therefore, careful planning and adjustments may be necessary throughout retirement to ensure a sustainable income stream.