Why sustainability matters

A retirement withdrawal amount can look reasonable as a percentage and still fail over a long horizon if inflation, return assumptions, or the retirement length are unfavorable.

This type of example helps separate a simple withdrawal-rate shortcut from a longer cash-flow stress test.

What this simplified model does not cover

The example does not model taxes, fees, changing withdrawals, guardrails, required distributions, Social Security timing, or sequence-of-returns volatility.

It is best used as an educational comparison page alongside broader retirement planning tools.