Purchasing power

Your account statement records dollars, not the groceries, housing, or other costs those dollars cover. More dollars do not necessarily mean more purchasing power. If your balance grows more slowly than prices, the money buys less despite the larger number on the statement. Comparing balances in the same period's dollars makes that change visible.

In a sentence

• "My balance rose to $10,500, but its purchasing power fell because prices rose faster."
• "I want to preserve my savings' purchasing power, not just keep the dollar balance unchanged."
• "We compare our retirement savings in today's dollars to understand their purchasing power."

How it's calculated

Purchasing power can be measured directly against a particular purchase or compared over time using a price index. For one item, divide your money by its price to find how many units you can afford. For a broader comparison, a price index tracks changes in the cost of a basket of goods and services.

1. Choose two dates and record the balance at each date, using the same account or set of assets and debts.
2. Choose a price index for the comparison, such as the US Consumer Price Index, and obtain its values for both dates.
3. Convert the later balance into the earlier period's dollars using the ratio below.
4. Compare that adjusted balance with the earlier balance to see whether purchasing power grew or fell.

Later balance in earlier dollars = later balance × (earlier price index ÷ later price index)

The result expresses both balances at the same price level. Deposits and withdrawals still affect the balances, so this comparison measures the purchasing power of what you hold, not necessarily the return your investments earned.

An example

Suppose you start with $10,000 and finish a year with $10,500, with no deposits or withdrawals. Over that year, assume a representative basket of goods and services rises from $100 to $110; these are illustrative figures, not reported inflation or a promised return.

The balance grows 5%, while the basket costs 10% more. Dividing $10,500 by 1.10 leaves about $9,545.45 in year-earlier dollars, so purchasing power falls about 4.55%.

Why it matters

Purchasing power changes how you read progress toward a future expense. A savings target based on today's price may no longer cover the purchase several years later. Updating the expected cost separates a larger account balance from actually getting closer to the goal.

A higher net worth can also buy less if consumer prices rise faster than the total. Comparing inflation-adjusted snapshots helps distinguish dollar growth from growth in buying capacity, but it does not turn property or investments into cash available for bills.

Purchasing power versus nominal dollars

Purchasing power measures what money buys; a nominal dollar amount records the number of dollars before adjusting for inflation. Your bank balance is a nominal figure, and it remains the amount in the account even when prices rise. An inflation-adjusted, or real, figure restates that amount at a chosen period's prices so you can make a like-for-like comparison. It is a comparison measure, not a different withdrawable balance.

Common questions

Can purchasing power fall while my account balance rises? Yes. When prices rise faster than the balance, the larger sum buys less than the smaller sum bought before. The example's $500 increase does not keep up with the higher cost of the same basket.

Does inflation affect everyone's purchasing power equally? No. A broad price index reflects a particular basket, while your spending mix may differ. If housing, medical care, or another large part of your own budget rises faster than the index, the index can understate the increase in your costs.

How does purchasing power relate to investment returns? A nominal rate of return measures investment gains and losses without adjusting for inflation; a real return includes that adjustment. For matching periods, real return equals (1 + nominal return) ÷ (1 + inflation rate) − 1, with rates written as decimals. Subtracting inflation from the nominal return is only an approximation.

Does lower inflation mean purchasing power recovers? Not by itself. Lower positive inflation means prices are still rising, only more slowly, so an unchanged sum still loses purchasing power. Whether your own money buys more depends on how its amount changes relative to the prices you pay.

Go deeper

• Is my net worth growing if prices are rising? compares snapshots in the same period's dollars to separate dollar growth from purchasing-power growth.
• The Retirement calculator projects what your retirement savings could grow to, what that is worth in today's dollars, and the monthly income it could support.