Withdrawal Strategies Compared: 4% Rule vs Constant % vs VPW
Side-by-side comparison of the three spend-down strategies: which guarantees stable income, which never runs dry, and which spends to zero on purpose.
Withdrawal Strategies Compared: 4% Rule vs Constant % vs VPW
The spend-down step addresses one question — the annual amount supportable from a portfolio balance at retirement — through four methods. Each makes a different tradeoff between income stability and portfolio longevity. The selection criterion is which limitation is acceptable.
The one-paragraph version
- Steady (4% rule): stable income, but the portfolio can run dry. Best when your spending is inflexible.
- Flexible (constant percentage): never runs dry, but your income swings with the market. Best when you can cut back in lean years.
- Spend-all (VPW): spends down to zero by your target age on purpose, with withdrawals that typically rise as you age. Best when you have a fixed horizon and no bequest motive.
- Guardrails (a fourth option in the module) hold spending steady and adjust only when the portfolio moves materially off plan.
Side by side
| 4% Rule | Constant % | VPW | |
|---|---|---|---|
| Year-1 withdrawal | Fixed % of starting balance | Fixed % of current balance | Amortized % of current balance |
| Later years | Same dollars + inflation | Same % of whatever remains | Rising % as horizon shrinks |
| Income stability | Stable | Volatile | Volatile, often rising |
| Can it hit $0 early? | Yes; this is the primary risk | No, by construction | No; reaches $0 exactly at the target age, by design |
| Success metric | % of scenarios lasting to end age | No success rate; watch the income band | No success rate; watch the income band |
| Bequest | Whatever survives | Whatever survives | Approximately $0 (specify a bequest target if required) |
How income, taxes, and floors change the answer
All four options take retirement income (Social Security, pension, rent), a tax rate on withdrawals, portfolio fees, a spending floor, and a leave-behind target:
- Income does not come from the portfolio. It adds to spendable income dollar-for-dollar. A $30k pension can move a 4% plan from a failing success rate to a passing one.
- Taxes reduce what you keep, not what leaves the portfolio: net = withdrawal × (1 − tax) + income.
- The spending floor is the applicable check for Constant % and VPW. Because neither method can fail by depletion, the reported metric is instead the frequency with which net income falls below the minimum required amount.
- The leave-behind target becomes the 4% rule's success bar, and for the other two we report the odds of clearing it.
Which should you use?
- Fixed costs dominate (mortgage, healthcare)? Start with Steady in the spend-down step. If its success rate is under ~90%, save more, spend less, or plan a lower rate.
- Flexible spending, value never depleting? Try Flexible and examine the withdrawal band. Assess whether the low-outcome years remain above required spending.
- Fixed horizon, want to spend it all? Run Spend-all (VPW). If the early-year withdrawals look too low, pair it with part-time income or a later end age.
- Want stability with a safety valve? Try Guardrails: steady income that only adjusts when your balance drifts far off track.
Still saving?
These strategies start from a lump sum. If accumulation is still in progress, define lifetime expenses first, then determine the requirement in the spend-down step, which models contributions followed by inflation-adjusted spending in one simulation.
Further reading: the 4% rule complete guide, the constant percentage guide, and the VPW guide.