What Bill Bengen Got Wrong About the 4% Rule (opens in new tab)

The FIRE movement is built around the 4% rule—the idea that you can safely withdraw 4% every year in retirement and not run out of money. It’s the mathematical formula upon which we’ve organized the past 10 years of our lives, and if math is our religion, the 4% rule is our scripture. Even though the Trinity Study has been cited as the inspiration behind the 4% rule, the actual person who deduced this rule is Bill Bengen, a financial planner/MIT engineer. Back in 1994, he analysed every 30-ye...