The consumer-price index, which measures what consumers pay for goods and services, rose 5.4% in September from a year earlier. Rising energy prices, supply-chain disruptions and an increase in spending have led to higher inflation across the country. While prices rose across the board for the year ended last month, the degree of change varied among different geographic regions and populations. Among the metropolitan areas surveyed, the largest and most urban places had some of the lowest price increases. Chicago saw an increase of 4.5%, and in the New York City area there was a 3.8% increase. The Northeast region’s rate...

The consumer-price index, which measures what consumers pay for goods and services, rose 5.4% in September from a year earlier. Rising energy prices, supply-chain disruptions and an increase in spending have led to higher inflation across the country. While prices rose across the board for the year ended last month, the degree of change varied among different geographic regions and populations. Among the metropolitan areas surveyed, the largest and most urban places had some of the lowest price increases. Chicago saw an increase of 4.5%, and in the New York City area there was a 3.8% increase. The Northeast region’s rate was nearly a percentage point below the overall national level.

To measure prices, the CPI focuses on what urban consumers pay for a hypothetical basket of goods and services. Those items are weighted to reflect the relative importance of components for a consumer living in a U.S. city. Rent accounts for 7.9% of the basket, while private transportation, including new and used vehicles and gasoline, makes up 14.1%. In the New York City area’s weighting, rent represents 12.1% of the basket, and private transportation is 9.2%. The design of the baskets for how people in cities spend their money, and how much income they spend on eating out or renting a car, is based on information from the Consumer Expenditure Surveys of urban consumers.

We used the surveys to compare how residents in rural areas, central cities and other urban areas budgeted their money, and we found that some of the spending categories with big differences between urban and rural areas also had big price increases, according to the CPI. The Consumer Expenditure Surveys define urban areas as the central city and attached locations inside a metropolitan statistical area, as well as other places with 2,500 or more people.

Rural consumers’ mean expenditures on gasoline and used cars and trucks were well above those of urban-area consumers in 2020. Households outside urban areas spent 37% more than the U.S. average on used cars and trucks, while spending in central cities was 9% lower than the average. The spending category saw one of the largest price increases in September’s CPI, up 24.4% compared with a year earlier.

On the other hand, rent, a heavyweight in central-city consumers’ budgets, saw some of the smallest price increases in September.

Consumers spent less and saved more as they lived through the Covid-19 pandemic, and stay-at-home orders altered spending habits last year. Apparel spending was down 24% in 2020, and spending on food away from home was 33% lower, according to the Consumer Expenditure Surveys. In 2021, as cities start to go back to their usual activities, price increases in those categories are likely to affect urban consumers more. In September, indexes for food away from home rose 4.7% from the same period a year earlier, compared with a 4.5% increase for food at home.

—Danny Dougherty and Gwynn Guilford contributed to this article.

Write to Max Rust at max.rust@dowjones.com and Ana Rivas at ana.rivas@wsj.com