The Consumer Price Index (CPI) Explained

When you hear that inflation was 3% last year or that prices rose faster than expected last month, the number often comes from the Consumer Price Index. CPI is one of the most important economic statistics in the United States, influencing everything from Social Security checks to tax brackets to interest rates. Here’s how it works and what it means for you.

What CPI measures

The Consumer Price Index measures the average change over time in the prices that urban consumers pay for a market basket of consumer goods and services. In simple terms, it tracks how much more or less a typical set of purchases costs over time.

The Bureau of Labor Statistics, part of the U.S. Department of Labor, publishes CPI every month. To build the index, BLS data collectors gather prices on tens of thousands of items from stores, service providers and rental housing units in cities across the country.

The most commonly cited version, CPI-U, represents the spending patterns of all urban consumers, which covers the large majority of the U.S. population.

What’s in the basket

The CPI basket includes the types of goods and services people buy, organized into major categories. These include housing, food and beverages, transportation, medical care, apparel, recreation, education and communication, and other goods and services.

Each category is weighted based on how much consumers spend on it, using data from government surveys of household spending. Housing makes up a large share of the index, reflecting how much of household budgets goes toward rent and the cost of homeownership. That’s why changes in housing costs have a big influence on overall CPI.

The BLS updates the basket and its weights periodically to reflect changes in what people buy, such as new technologies and shifting spending habits.

Headline versus core CPI

Headline CPI includes everything in the basket. It reflects the full cost of living, including food and energy prices.

Core CPI excludes food and energy prices. These categories can be volatile, swinging sharply because of weather, global events or supply disruptions. By excluding them, core CPI aims to show underlying inflation trends more clearly. Economists and policymakers often watch core CPI to judge whether inflation is becoming persistent.

Neither measure is better than the other. Headline CPI reflects what households actually pay, while core CPI helps identify longer-term trends.

How CPI is used

CPI affects many parts of the economy and your finances. Cost-of-living adjustments for Social Security benefits are based on a CPI measure called CPI-W, which reflects the spending of urban wage earners and clerical workers. When CPI-W rises, Social Security benefits generally rise the following year.

Many tax provisions, including federal income tax brackets and the standard deduction, are adjusted each year for inflation using a CPI measure. This prevents inflation from pushing people into higher tax brackets even if their real income hasn’t changed.

Some wages, union contracts, leases and other agreements include clauses tied to CPI, adjusting payments automatically as prices change.

Treasury Inflation-Protected Securities, known as TIPS, are government bonds whose principal is adjusted using CPI. As inflation rises, the principal increases, protecting investors’ purchasing power. Series I savings bonds also use CPI in calculating their interest rate.

CPI and the Federal Reserve

The Federal Reserve closely watches inflation when setting interest rates. Although the Fed’s preferred inflation measure is the Personal Consumption Expenditures price index, CPI is released earlier and is widely followed by markets. High CPI readings can increase expectations that the Fed will keep rates higher, affecting borrowing costs for mortgages, car loans and credit cards.

Your personal inflation rate may differ

CPI is an average, and your personal inflation rate depends on what you actually buy. A household that drives long distances may feel gas price changes more strongly. Renters may feel housing costs more than homeowners with fixed-rate mortgages. Older adults may spend more on medical care, while families with young children may spend more on child care and education.

To estimate your own inflation, compare your spending in key categories this year with last year. Knowing which costs are rising fastest for you can help you adjust your budget.

CPI versus PCE

The Federal Reserve’s preferred inflation measure is the PCE price index, published by the Bureau of Economic Analysis. It covers a broader range of spending, including costs paid on behalf of consumers, such as employer-provided health insurance, and adjusts more readily when people switch to cheaper alternatives. PCE inflation often runs slightly lower than CPI.

Using CPI in your own planning

Understanding inflation helps you make better financial decisions. If inflation is running high, it’s important that your savings earn a competitive rate, that your raises keep pace with rising costs and that your long-term investments have the potential to outgrow inflation over time.