Comparison
4% rule vs guardrails
The 4% rule keeps spending steady. Guardrails let it adjust with markets. Here’s how they compare on the same savings, through every market since 1928.
Historical success with $45,000 a year from $1,000,000: fixed spending lasted in 58 of 69 starts; guardrails lasted in 68 of 69 starts.
| Fixed spending | Guardrails | |
|---|---|---|
| Lasted 30 years (history) | 84% | 99% |
| Lasted (2,000 simulated markets) | 86% | 95% |
| Lowest yearly spending, starts that lasted | $45,000 | $36,000 |
| Typical total spending, whole retirement | $1.35M | $1.56M |
| Typical money left at the end | $1.17M | $1.09M |
| Years sold investments right after a drop | 7.9 on average | 8.1 on average |
Selling right after a stock decline locks in losses. The last row counts those years in a typical retirement.
- Fixed spending
- Guardrails
What this means
With $45,000 a year from $1,000,000 (4.5%), fixed spending lasted 30 years in 84% of historical starts and guardrails in 99%.
Among starts that lasted, fixed spending kept spending highest in its leanest year, never below $45,000.
No plan wins on every measure. Plans that adjust spending protect your savings but ask you to accept some lean years; fixed plans keep spending steady but need a lower starting rate to hold up in the worst markets. The right choice depends on how much flexibility your budget really has.
How each one works
4% rule
Withdraw 4% in year one, then raise the dollar amount with inflation every year. Spending never changes because of markets. Simple and predictable, but it must be set low enough to survive the worst retirement on record.
Guardrails
Start with a withdrawal rate, then watch it each year. If a market drop pushes it 20% above where you started, cut spending about 10%. If growth pulls it 20% below, give yourself a 10% raise. A floor limits how low cuts can go.
The trade-off
Guardrails buy a higher starting income and better odds in exchange for occasional cuts. The 4% rule buys certainty of spending in exchange for a lower start and the small chance that the money runs out in a very bad sequence.
For many retirees the deciding question is simple: if markets fell 30%, could you trim spending by about 10% for a year or two? If yes, guardrails let you spend more in all the years when that never happens.
Assumptions
- Fixed and guardrail plans hold 60% stocks and 40% 10-year Treasuries. Bucket plans keep 4 years of withdrawals in Treasuries and invest the rest 80% in stocks.
- Guardrails: cut spending 10% when the withdrawal rate rises 20% above its start, raise 10% when it falls 20% below, floor at 80% of starting spending.
- History tests every 30-year stretch since 1928. The simulated figure stitches together random 5-year blocks of real history (2,000 runs). No taxes or fees.
New to a term? See the retirement income glossary.
Common questions
Are guardrails better than the 4% rule?
Historically, guardrails lasted in more starts and supported higher starting spending, at the cost of occasional spending cuts. Neither is better for everyone.
What are the Guyton-Klinger guardrails?
A set of withdrawal rules published by Jonathan Guyton and William Klinger in 2006 that cut or raise spending when the withdrawal rate crosses upper or lower limits. Our guardrails follow the same idea.
How often do guardrails cut spending?
It depends on your starting rate. At around 4.5%, many historical retirements saw a few cuts over 30 years; some saw none. The comparison chart shows cuts for the replayed start year.
Related tools
How we calculate this
Each plan runs through the same historical stretches and the same simulated markets, so the only difference is the withdrawal rules. Bucket plans withdraw from cash and refill it only when investments are within 5% of their previous high.
Data: S&P 500 total returns, 10-year Treasury and 3-month Treasury bill returns as compiled by Aswath Damodaran (NYU Stern), and CPI-U inflation from the U.S. Bureau of Labor Statistics, 1928–2025 (2025 preliminary). Read the full methodology and limitations.