Inflation and Real Returns

Say your $200 becomes $210 in a year. You have more money. Can you buy more with it?

Suppose a basket of everyday purchases costs $100 when you start and $106 a year later. At first, your $200 buys two baskets. A year later, two baskets cost $212. You are $2 short, despite the gain.

Your account has more dollars, but those dollars buy less. Investment progress has two measures: the number on the statement and what it can pay for.

More dollars can still buy less

Purchasing power is the quantity of goods and services your money can buy. Here, you measure it in baskets instead of dollars.

Inflation is a general rise in prices. A more expensive coffee alone does not tell you whether prices are rising across the economy.

Your nominal return is your investment's percentage gain or loss before adjusting for inflation. The $10 gain on $200 is 5%. Your real return measures the percentage change in purchasing power.

You start with $200 / $100 = 2 baskets. You finish with $210 / $106, or about 1.98 baskets. Buying power fell by about 0.94%.

A gain on your statement can still mean a smaller shopping basket.

Divide the two growth factors

The balance grew to 1.05 times its starting value. The basket's price grew to 1.06 times its starting cost. These are growth factors: one plus each rate, written as a decimal.

Divide them to see which one pulled ahead:

Use 0.05 for 5% and 0.06 for 6%, and match the periods: one year's investment return needs that same year's inflation. Subtract 1 from the fraction to get the return:

Real return = (1.05 / 1.06) − 1 ≈ −0.94%.

The fraction is just under 1, so you kept slightly less than your starting buying power. Subtracting 1 leaves the gain or loss.

Subtracting inflation is a shortcut. Here, 5% − 6% gives −1%, close to the exact answer. At larger rates the shortcut can mislead: 50% growth and 25% inflation give a 20% real return (1.50 / 1.25 − 1), not 25%.

Include dividends or bond interest alongside price changes in the nominal return. Your own deposits are not investment gains.

The gap grows over time

Say $10,000 grows 5% a year while prices rise 3% a year for 20 years. Keep all gains invested, make no deposits or withdrawals, and leave out fees and taxes.

With compounding, the balance and its buying power both grow. The lines separate because each year's dollar buys less.

After 20 years, $10,000 × 1.05²⁰ is about $26,533. Divide by the price growth over those years, 1.03²⁰, and the balance buys what $14,691 bought at the start.

Both lines describe the same investment. The gap is not a fee or cash leaving the account. It is a change of units, from dollars at each date to dollars with the starting year's buying power.

The real annual return is 1.05 / 1.03 − 1, about 1.94%. Cash savings can earn interest too: their buying power grows if the return beats inflation and shrinks if it falls behind.

Put the goal in matching dollars

A future balance and a spending goal need matching dollars. Comparing a future balance with an unchanged starting-year target can make a shortfall look like success.

The two baskets give you two ways to make the comparison:

• Future dollars: The baskets cost $212 in a year. The $210 balance falls short.
• Starting-year dollars: The target is $200 of buying power. The balance is worth $210 / 1.06, or about $198.11, in those same dollars. It still falls short.

Either comparison gives the same answer. Changing the units does not change whether you can afford the purchase.

A useful goal names both its date and its dollars: “$200 of September 2026 buying power, needed in September 2027.” That fixes what you want to buy; the future dollar cost still depends on inflation.

Optional: what US history shows

The asset-class comparison used these US returns for 1928–2024. The new column measures what the growth bought after inflation. Each annualized rate describes the same full period.

These calculations retain income and exclude fees and taxes. All three beat inflation over the full sample; that does not promise protection in every year, country or future period.

The adjustment uses CPI-U, the Consumer Price Index for All Urban Consumers, a broad US consumer-price measure. Your own spending mix may rise in price faster or slower than that average basket.

Some government securities do adjust for inflation by contract; Treasuries explains those terms.

The bill series barely grew in purchasing power. A positive dollar return and meaningful spending progress are different things.

A future price tag still needs a deadline. The next lesson uses your time horizon to match that deadline to the risk your goal can carry.

In short

• Nominal returns count dollars; real returns track what those dollars buy.
• Divide one plus the nominal return by one plus inflation, then subtract 1, for the exact real return.
• Give a future goal a date and say whether its amount is in current or future dollars.
• A historical return that beat inflation does not guarantee buying power at your deadline.