The 4% Rule — Safe Withdrawal Rate
The 4% safe withdrawal rate (SWR) emerged from William Bengen's 1994 research, later confirmed by the Trinity Study: a retiree withdrawing 4% of their initial portfolio value in the first year of retirement, then adjusting that amount for inflation annually, has historically had a very high probability (95%+) of not running out of money over a 30-year retirement period — based on historical US stock and bond returns from 1926 onward. Application: if you need $60,000/year from your portfolio, the required savings is $60,000 / 0.04 = $1,500,000 (the '25x rule' — 25 times annual spending). The 4% rule assumes a diversified portfolio (approximately 60% stocks/40% bonds) and a 30-year retirement horizon. For longer retirements (early retirement at 40 targeting 50+ years of withdrawals), a more conservative 3–3.5% withdrawal rate is recommended. Criticisms of the 4% rule: it is based on historical US returns that may not repeat (particularly with low current bond yields); it does not account for variable spending in retirement (most retirees spend more in their active early retirement years and less in later years); and it is based on a fixed withdrawal percentage rather than a dynamic strategy. Updated research suggests a flexible withdrawal approach (spending less in market downturns, more in strong markets) outperforms fixed-percentage withdrawal by preserving capital in bad sequences.