Retirement Accumulation vs. Retirement Income
Plain English
While you're working and saving, the main question is how fast your money grows. Once you retire and start withdrawing, the main question shifts to whether your money will last — and that's a different, often harder problem.
What is it?
Accumulation is the phase of building retirement savings through contributions and investment growth. Decumulation (retirement income) is the phase of withdrawing from that pool to fund living expenses, generally without further contributions.
Why does it matter?
The math and the risks are genuinely different between the two phases — sequence-of-returns risk, for example, barely matters during accumulation but matters a great deal during decumulation (see the Risk Education module).
How does it work?
Accumulation tools (like the Retirement or 401(k) calculators) project a single ending balance from contributions and an assumed return. Decumulation tools (like the Retirement Income calculator) simulate withdrawals against a balance that's still trying to grow, year by year, to see whether and how long it lasts.
Risks and limitations
A large accumulated balance does not, by itself, guarantee that it will support a given withdrawal rate for as long as needed — that depends on the withdrawal rate, investment returns, inflation, and how long the money needs to last.
Questions to ask a professional
Have I planned for both phases separately, or only projected accumulation and assumed the rest works out? What withdrawal rate am I assuming, and how sensitive is my plan to that assumption?