Sensitivity-analysis

A mortgage rate below an expected investment return does not automatically mean you should invest. Compare after-tax returns, liquidity, and household resilience with this repeatable decision matrix.

Using one set of spending, portfolio, and return assumptions, compare how 20%, 40%, and 60% work-hour reductions affect a FIRE timeline and identify the cash-flow threshold.

The point of annual FIRE recalculation is not to predict the future more precisely. It is to identify which assumptions can actually break your plan. This guide walks through return, inflation, and withdrawal-rate sensitivity using a practical household example.