The 4% rule for retirement withdrawals, and when it breaks down

If you've spent any time in personal finance circles, someone has mentioned the 4% rule. It's become retirement planning shorthand: save 25x your annual expenses, withdraw 4% a year, and you'll never run out of money. It's simple, memorable, and mostly right. The "mostly" part is worth examining.

Where it comes from

In 1994, financial planner William Bengen analyzed historical market data and found that a 4% initial withdrawal rate, adjusted for inflation, survived every 30-year period from 1926-1992, assuming a 50/50 stock/bond portfolio.

The "worst case" scenario was retiring in 1966, just before a brutal 1973-74 bear market. Even then, 4% survived.

How it works in practice

You retire with $1,000,000.

• Year 1: Withdraw $40,000 (4%)
• Year 2: Inflation is 3%, so withdraw $41,200 (last year's amount × 1.03)
• Year 3: Inflation is 2%, so withdraw $42,024 ($41,200 × 1.02)

You adjust for inflation regardless of portfolio performance. If the market drops 20%, you still take $42,024.

When the 4% rule breaks down

Lower expected returns: Bond yields are lower than historical averages. Some researchers suggest 3.5% is safer.

Longer retirements: The rule assumes 30 years. If you retire at 55, you need money to last 40+ years.

Sequence of returns risk: If you retire into a bear market, withdrawing 4% while your portfolio drops can deplete it faster than historical averages suggest.

Lifestyle inflation: If your spending increases faster than CPI inflation, 4% may not be enough.

The 4% rule variants

The 3.5% rule: More conservative, higher success rate over 40+ years.

The dynamic rule: Adjust withdrawals based on portfolio performance (cut spending in down years, increase in up years).

The guardrails approach: Start at 5%, but if portfolio drops below X%, cut to 4%. If it grows above Y%, increase to 6%.

What about Social Security?

The 4% rule assumes zero other income. In reality, most retirees have Social Security, pensions, or part-time work.

If Social Security covers 50% of your expenses, you only need your portfolio to cover the other 50%, which significantly improves the odds.

The bottom line

The 4% rule is a starting point, not gospel. It worked historically, but future returns may differ.

More conservative approaches:

• Use 3.5% if retiring before 60
• Build in flexibility to reduce spending during bear markets
• Consider part-time work in early retirement years
• Delay Social Security to age 70 for higher payouts

The 4% rule gives you a ballpark estimate of how much you need. For $40,000/year in retirement spending, you'd need a $1,000,000 portfolio ($40k / 0.04).

But don't treat it as a guarantee. Markets don't care about historical averages.