If a carton of eggs costs more this month than last, that is a price increase for one product. If the average price of a broad basket of goods and services rises over time, that is inflation. Deflation is the reverse: a sustained decline in the general price level. The distinction matters because a sale on one shelf is not an economy-wide trend, and inflation cooling does not mean prices have returned to where they were.
One price is not the whole price level
A store may discount a television, or a grocery item may become cheaper after a temporary supply improvement. That is a change in the price of an individual product. Inflation and deflation describe movement across a wider set of consumer purchases, measured with an index that combines many prices.
The Consumer Price Index, or CPI, tracks the average change over time in prices paid by urban consumers for a representative basket of goods and services. Its categories include housing, food, transportation, medical care and recreation, with price changes weighted by their importance in spending Bureau of Labor Statistics. The basket makes it possible to distinguish a broad movement from a single bargain. It still represents an average, not every household’s exact experience.
Slower inflation still leaves prices higher
Suppose a broad index rises by 5 percent one year and 2 percent the next. Inflation has slowed: prices are rising more slowly. They have not generally fallen. The price level is higher than before either increase, unless a later period brings an actual decline.
That difference helps explain why easing inflation can feel incomplete at home. A family may welcome smaller increases in the overall basket while still paying more than it used to for rent, meals or transportation. Individual prices can fall during this period, but such declines do not erase the broader increase. The CPI measures an average of price changes, and BLS cautions that it may not match a particular person’s spending pattern Bureau of Labor Statistics.
Deflation means a broad decline
Deflation occurs when the general price level falls over time. It is not simply a month when one index or one category dips. A sustained decline across a broad measure is the key idea; an isolated drop in phone service or used-car prices is not enough to describe the whole economy.
The pattern within the September 2026 CPI illustrates why category-level evidence needs context: communication prices fell that month, while the all-items index rose 0.6 percent on a seasonally adjusted monthly basis and 3.7 percent over the 12 months through September Bureau of Labor Statistics. The movement in one category did not amount to deflation. The same release reported food prices unchanged for the month, while shelter rose 0.4 percent.
Read the index and the time period
When a report uses the word inflation, check which index it means and whether the comparison is monthly or year over year. The CPI measures consumer price changes for its defined population and basket. The Personal Consumption Expenditures price index is a separate measure of prices for goods and services purchased by people in the United States or on their behalf, and it can reflect changes in consumer behavior Bureau of Economic Analysis. Their reported rates are not interchangeable.
For example, the September 2026 release showed CPI inflation of 3.7 percent over the year, while the PCE index showed 3.6 percent for that period Bureau of Labor Statistics Bureau of Economic Analysis. The small difference does not mean one measure describes every household better in every circumstance; they use different approaches. The practical test is simple: ask whether the broad index is rising or falling, then note the period and measure. A discount is local. Lower inflation is slower growth in prices. Deflation is a broad decline.
Sources & further reading
- Consumer Price Index questions and answers ↗Bureau of Labor Statistics
- Personal consumption expenditures price index ↗Bureau of Economic Analysis
- September 2026 Consumer Price Index ↗Bureau of Labor Statistics
