The Base Case: Sarah’s Retirement Plan
Sarah’s inflation-adjusted retirement planning base case
| Factor | Value |
|---|---|
| Current age | 45 |
| Retirement age | 65 |
| Years to retirement | 20 |
| Current monthly expenses | $5,000 |
| Expected inflation rate | 3% |
| Inflation-adjusted monthly need at 65 | $9,031 |
| Retirement duration (to age 90) | 25 years |
| Annual portfolio withdrawal (age 65) | $108,372 |
| Required portfolio at 65 (4% rule) | $2,709,300 |
Why Sarah Needs More Than She Thinks
Sarah thinks she needs $5,000/month to retire. That’s true in today’s dollars. But in 20 years at 3% inflation, $5,000/month has the purchasing power of only $2,776 in today’s money — she actually needs $9,031/month in nominal terms. Furthermore, that $9,031 at age 65 will need to increase to $18,425/month by age 90 to maintain the same real standard of living.
A $100,000 annual retirement income at age 65, with 3% annual inflation, needs to be $200,743 per year by age 90 to maintain the same purchasing power. A fixed-income annuity provides stable nominal income but declining real income. Portfolios with inflation-adjusted withdrawal strategies are essential for maintaining real spending power through a 25+ year retirement.
Inflation’s Impact on the 4% Rule
The 4% rule (withdraw 4% of portfolio in year 1, increase annually with inflation) was designed with inflation in mind. The original Trinity Study (1998) using historical data including inflationary periods found this withdrawal rate sustainable over 30 years for balanced portfolios. But the rule assumes inflation-adjusted withdrawals — meaning the dollar amount withdrawn increases each year, requiring a large enough portfolio to sustain this.
Inflation’s impact on required retirement portfolio by monthly spending need and inflation rate
| Today’s Monthly Need | Inflation Rate | Monthly Need in 20 Years | Required Portfolio (4% Rule) |
|---|---|---|---|
| $3,000 | 2% | $4,459 | $1,338,300 (yr 1 withdrawal $53,508) |
| $4,000 | 2% | $5,946 | $1,783,800 |
| $4,000 | 3% | $7,224 | $2,167,200 |
| $5,000 | 3% | $9,031 | $2,709,300 |
| $6,000 | 3% | $10,837 | $3,251,100 |
| $5,000 | 4% | $10,955 | $3,286,500 |
Inflation-Proof Retirement Income Sources
Best sources for inflation-protected retirement income: (1) Social Security — COLAs adjust benefits annually with CPI-W; (2) TIPS bond ladder — principal adjusts with CPI; (3) Stock portfolio — dividends and capital gains historically outpace inflation long-term; (4) Real estate rental income — rents typically rise with inflation; (5) Inflation-adjusted annuities (expensive but provide certainty). Worst: fixed-dollar annuities, traditional pension without COLA, and cash savings.
Calculate Your Inflation-Adjusted Retirement Need
Enter your current monthly expenses and years to retirement to see the inflation-adjusted future amount you’ll need.