The 4% rule, and its fine print

Almost every FIRE calculation traces back to one number. It's worth knowing where it came from, because the shorthand version has drifted a long way from what the research actually said.

Where it came from

In 1994 the financial adviser William Bengen tested how much a retiree could withdraw annually without running out of money, using historical US market returns going back to 1926. He found that a portfolio split between stocks and bonds could sustain an initial withdrawal of about 4% of its value, adjusted upward for inflation each year, across every 30-year window in that history — including retirements that began right before major crashes.

A group of professors at Trinity University ran a related study a few years later, and the combined finding became known as the 4% rule.

What it implies

Inverted, 4% gives the number FIRE communities quote constantly: you need roughly 25 times your annual expenses. Spending ₹12 lakh a year implies a target near ₹3 crore. The multiple is simply 1 divided by the withdrawal rate — a 3% rule implies 33 times, a 5% rule implies 20 times.

The fine print people drop

It was built on 30-year retirements. Someone retiring at 40 may need the money to last 50 years, and the failure rate rises as the horizon lengthens.

It was built on US market history. That century was unusually kind. Studies applying the same method to other countries generally produce lower safe rates.

It assumed a specific portfolio and no fees. Real costs, taxes, and different asset mixes all shift the number, usually downward.

It assumed rigid spending. The rule withdraws the same inflation-adjusted amount whether markets rose or fell. Real people adjust, and flexible spending materially improves the odds.

Indian conditions differ. Higher historical inflation and a different tax treatment of long-term gains both matter, and neither is in the original study.

How to hold it

As a planning starting point with a wide error bar, not a guarantee. Many people now work with 3% to 3.5% for long retirements, or keep the 4% figure but plan to spend less in bad years. Bengen himself has revisited the number more than once. Treating it as a fixed law is the one reading the research does not support.

Nothing here is investment advice. See the disclaimer.