What is Purchasing Power?

Purchasing power describes what a dollar actually buys in the real economy. It moves in inverse relation to inflation: when prices rise, each dollar commands fewer goods and services. The BLS provides a CPI Inflation Calculator that lets consumers compare the purchasing power of a dollar amount between any two years going back to 1913.

Purchasing power erosion is the central risk of holding too much cash for too long. A savings account earning 1% in a 3% inflation environment loses 2% of its real value each year. Over a 30-year retirement, that compounds into a dramatic reduction in living standards unless assets are invested in instruments that historically outpace inflation.

Preserving purchasing power is the baseline goal of long-term investing, not maximizing returns in any single year, but ensuring that the portfolio’s real (inflation-adjusted) value grows over time. Treasury Inflation-Protected Securities (TIPS) and Series I Savings Bonds are two federal instruments designed explicitly to preserve purchasing power by adjusting principal and interest payments for CPI-measured inflation.

To evaluate investment options effectively, individuals must focus on the difference between nominal returns and real returns. The real rate of return is calculated by subtracting the inflation rate from the nominal rate of return (Real Return = Nominal Return - Inflation Rate). If an asset earns a nominal return of 5% in a year where inflation is 4%, the real growth in purchasing power is only 1%. On a macroeconomic scale, economists use the concept of Purchasing Power Parity (PPP) to compare economic productivity and standards of living between countries by adjusting for local price differences. Ultimately, if household wages do not rise at a rate equal to or greater than the rate of inflation, the household experiences a reduction in real income, meaning their labor commands fewer goods and services each year despite having a stable or increasing nominal salary.