What is the Safe Withdrawal Rate? The Safe Withdrawal Rate (SWR), popularized as the “4% rule”, is the annual percentage of a retirement portfolio you can spend in year one (then adjust for inflation) with a high probability of not running out of money over a 30-year retirement. It was derived from the Trinity Study analyzing US market history from 1926 onward.
Worked example: a $1,000,000 portfolio supports $40,000 in year-one withdrawals; in year two you withdraw $40,000 × (1 + inflation). If inflation was 3%, year-two withdrawal is $41,200, regardless of portfolio performance. Historically, a 50/50 to 75/25 stock/bond mix survived every 30-year window at 4%. For early retirees facing 40–60 year horizons, many practitioners lower the SWR to 3.25–3.5% to reduce failure risk.
The 4% rule is a planning heuristic, not a guarantee. It assumes US market returns continue, low fees, and tax efficiency. Sequence-of-returns risk, a crash in the first five years, is the primary failure mode. Variable withdrawal strategies (guardrails, CAPE-based rates) often outperform static 4% in real-world retirements.