Forgetting Inflation in Planning
Forgetting Inflation in Planning
You plan to retire with $1 million in 30 years. You reach the goal and retire. But 30 years of 3% inflation means that $1 million has the purchasing power of $400,000 in today's dollars. Your plan was based on nominal returns, not real returns. You can't afford your intended lifestyle.
Key takeaways
- Inflation erodes purchasing power: 3% annual inflation halves the value of money every 24 years; your $1 million in 30 years buys $410,000 worth of 2026 goods
- Investment returns are usually quoted as "nominal" (3% total return), not "real" (real return after inflation); confusing the two leads to severe under-planning
- Historical real stock returns: 5–6% per year (after inflation); real bond returns: 1–2% per year; real cash: 0% (inflation eats it)
- A retirement plan that assumes $100,000 per year needs $300,000+ per year in 30 years, due to inflation alone
- Inflation-protected strategies (TIPS, inflation-indexed bonds, commodities) are part of a complete plan, but most investors skip them
The arithmetic of inflation
Inflation is the rate at which the general price level of goods and services rises. The U.S. has averaged about 3.1% annual inflation over the past 50 years. Some years it's 0.5% (2015), some years it's 9% (2022). On average, 3%.
At 3% annual inflation, the purchasing power of money decays as follows:
| Years | Inflation | Purchasing Power | Example: $1M becomes |
|---|---|---|---|
| 0 | 0% | 100% | $1,000,000 |
| 10 | 3%/yr | 74% | $740,000 |
| 20 | 3%/yr | 55% | $550,000 |
| 30 | 3%/yr | 41% | $410,000 |
| 40 | 3%/yr | 31% | $310,000 |
This is the core mistake. An investor who saves $1 million by age 55 and retires, expecting that $1 million to last 30 years, will find that it no longer buys what $1 million bought at age 55. The lifestyle they intended is impossible.
Nominal vs. real returns
Investment returns are usually quoted as "nominal": the total dollar gain, not adjusted for inflation.
Example: You buy a bond paying 4% per year. Over a year, you earn 4% nominal return. But if inflation was 3%, your real return is only 1% (4% - 3% = 1%). You made money in dollars, but you lost purchasing power.
Many investors plan assuming nominal returns:
- "Stocks return 10% per year, so my $50,000 will become $1.3 million in 30 years."
But the correct calculation is:
- "Stocks return 7% real (after inflation), so my $50,000 will become $0.8 million in 2026 dollars."
Or, if you want the nominal value:
- "Stocks return 10% nominal, so my $50,000 will become $1.3 million in 2056 dollars. But 2056 dollars are worth only $0.53 in 2026 dollars, so I have $0.7 million in purchasing power."
(Note: these are simplified; real inflation varies year to year.)
The difference is enormous. A plan based on nominal returns without adjusting spending expectations is a plan that will fail.
The retirement planning disaster
A 35-year-old plans to retire at 65 with a nest egg that can generate $100,000 per year in spending.
She calculates: "If I need $100,000 per year for 30 years, I need $3 million (ignoring growth, just $100K × 30). I'll aim for $3 million."
At 65, she reaches $3 million. She retires.
But wait. In 30 years, at 3% annual inflation, $100,000 is no longer enough. She needs to spend $240,000 per year to have the same lifestyle she planned for.
Her $3 million, if invested at 5% real return, generates $150,000 per year. After inflation, she can spend $150,000 / 1.03 = $146,000 in real terms (roughly). She needs $240,000. She's short by $94,000 per year, or 39% of her spending goal.
The correct plan:
- Today (age 35): I need $100,000 per year for lifestyle.
- At retirement (age 65): I'll need $100,000 × 1.03^30 = $242,000 per year.
- Over 30-year retirement (ages 65–95): I'll need an escalating amount, $242K, $249K, $257K, ..., as inflation continues.
- Average need: about $340,000 per year in nominal terms.
- To generate this safely: I need $340,000 / 0.05 (real return) = $6.8 million in today's dollars (or about $16 million in future dollars).
The gap between the naive plan ($3 million) and the correct plan ($6.8 million) is $3.8 million. The investor is underfunded by 56%.
This is not theoretical. It's a common retirement planning failure: people retire with a number they calculated decades earlier without adjusting for inflation, find that it's not enough, and either work longer or reduce spending.
Real returns vs. nominal returns
Here's a rough guide to real returns (after inflation):
Stocks: 5–6% real. Historically, U.S. stocks have returned about 10% nominally and 7% really (real return = nominal return - inflation).
Bonds: 1–2% real. Bonds typically return 3–4% nominally and 1–2% really, depending on duration and type.
TIPS (Treasury Inflation-Protected Securities): By definition, the yield you see is the real return. A 2% TIPS yield gives you 2% real, guaranteed by the Treasury. The face value adjusts for inflation.
Cash/money market: 0% real. Whatever the current rate is, subtract inflation, and you'll see cash returns are zero or slightly negative in real terms.
This is why stocks are necessary for long-term investing. Bonds provide stability, but only stocks provide real return that can grow wealth across decades.
Adjusting your plan for inflation
Step 1: Estimate your annual spending need in today's dollars.
If you're 35 and plan to retire at 65 spending $80,000 per year, write down the $80,000 as your baseline.
Step 2: Inflate it forward to retirement age.
At 3% inflation over 30 years: $80,000 × 1.03^30 = $194,000. You'll need to generate about $194,000 per year from your portfolio in the year you retire.
Step 3: Calculate the portfolio needed.
If you can safely withdraw 3.5% from your portfolio per year (a conservative estimate based on historical data), you need: $194,000 / 0.035 = $5.5 million in future dollars, or about $2.3 million in today's dollars.
Step 4: Build backward from retirement.
At 35, with 30 years to invest, and targeting $5.5 million in future dollars, how much do you need to save annually? If you earn 7% real return (roughly the stock market's historical real return), you need to save about $75,000 per year in today's dollars to reach the goal.
This is a serious amount, but it's what a realistic plan requires.
The inflation-protection strategy
Some investors include inflation-protection in their portfolio:
- TIPS (Treasury Inflation-Protected Securities): Bonds that adjust face value for inflation. A 2% TIPS yield plus inflation equals your total return, preserving real value.
- Commodities: Oil, metals, and agricultural commodities tend to preserve value during inflation, though they're volatile.
- Dividend growth stocks: Stocks of companies that raise dividends every year tend to keep pace with inflation.
- REITs: Real estate typically preserves value in inflation.
A portfolio that's 70% stocks, 20% bonds, and 10% TIPS or commodities is more inflation-resilient than a portfolio of 70% stocks and 30% bonds (traditional 70/30).
Most first-time investors skip this complexity. But it becomes important for longer horizons (20+ years) and in high-inflation environments.
The inflation math flowchart
Related concepts
Next
Forgetting inflation is a planning mistake that surfaces decades later, when it's too late to fix. But there's a deeper mistake that causes all the others: having no written plan at all. A plan forces you to name numbers, think through assumptions, and commit to a path. Without it, you're improvising—and improvisation under market stress is how all the previous mistakes happen.