While saving, contributions flow into the investment pot. In retirement, withdrawals can flow out. That changes the effect of a market fall: selling to meet a bill can remove units that would otherwise remain invested.

Risk still matters during accumulation, especially near the date you need the money. Retirement adds a particular problem: withdrawals can make the order of returns important, even when two histories have the same average.

This lesson explains that mechanism so you can ask better questions about a retirement plan; it does not set a withdrawal rate for you.