#safe withdrawal rate

Two retirees can earn the identical compound return over thirty years and finish $2.7 million apart. One of them can go broke. Nothing separates them except the order the returns showed up in, and that is a much bigger deal than almost anyone budgets for.

Same question, two credible answers, 0.8 percentage points apart. On a $1 million portfolio that is $8,000 a year of spending. The gap is not a disagreement about facts, it is a disagreement about whether to forecast the future or replay the past, and knowing which you are relying on matters more than the number.