Using ‘per capita’ to describe data

If you report on economic research and government reports, you’ve almost certainly encountered the statistical term “per capita,” a Latin phrase that means “by heads” or, essentially, “per person.”

A country’s gross domestic product, a popular measure of economic health, often is expressed in terms of per capita — the value of goods and services produced by that nation per individual within the population. The United States’ GDP was just under $26.5 trillion during the first quarter of 2023, according to the U.S. Bureau of Economic Analysis. The GDP per capita: $79,148.            

Scholars, statisticians and government officials also use the term when examining data for a range of policy issues, including public health, education funding, local crime and public transportation usage. A researcher might, for example, track per capita sugar consumption in a certain city to gauge how much sugar each resident consumes in a given year, on average.

Although per capita is a specific type of rate, news outlets sometimes use it incorrectly to describe other rates. Also, journalists frequently report on data without breaking it down per capita, even when doing so would provide audiences with crucial context.

One of the most common mistakes news outlets make is using “per capita” to describe a number per 1,000, 10,000 or 100,000 people. For instance, if a government report estimates the number of police officers working in a particular state is 2.3 officers for every 1,000 residents, it would be incorrect to report this as the number of officers per capita. The per capita rate would be 0.0023 officers per resident.

To help us explain the right and wrong ways to use the term in news coverage, we teamed up with two experts — economist Steve Landefeld, the former, longtime director of the U.S. Bureau for Economic Analysis, and statistician Jing Cao, a professor in the Department of Statistics and Data Science at Southern Methodist University.

They suggest journalists keep these four things in mind:

Per capita figures represent the average number of something for all people within a population, Landefeld and Cao explain.

If you were to report on per capita health care expenditures for each state, for instance, you’d provide audiences with the average amount of money each person spends on health care, by state. Per capita health care spending in 2020 ranged from $7,522 in Utah to $14,007 in New York, a report from the U.S. Centers for Medicare & Medicaid Services shows.

Government agencies in the U.S. report many types of data on a per capita basis. But if they don’t do that for the data you’re examining, Landefeld and Cao recommend doing the math yourself. To calculate per capita, take the number you’re interested in and divide it by the population involved.

“It’s a pretty straightforward concept,” Cao says. “You just need to know the population.”

Here’s a quick demonstration. Let’s say a city government reports that its residents threw away 55,200 tons of garbage in 2021. To find out how much garbage each resident threw out, on average, you’ll need to look up or ask for the city’s population that year. Let’s say 710,000 adults and children lived in that city in 2021.

Here’s the per capita calculation:

Tons of garbage per capita = 55,200 tons of garbage/710,000 residents = 0.08

To help audiences better visualize the amount thrown out, consider reporting it in pounds per person, instead of tons. In the U.S., there are 2,000 pounds in a ton. In this city, each resident threw away an average of 160 pounds of trash in 2021.

Researchers and public health officials often report the rate of COVID-19-related deaths as the number of deaths per 100,000 people across a country or other geographic region. Some news outlets have incorrectly described these rates as “per capita” death rates.

In recent years, journalists have also incorrectly referred to rates of identity theft, shootings, home sales and the concentration of fast-food restaurants in an area as “per capita” rates. Some of that coverage focuses on data expressed as a number per 10,000 people.

“When the number you’re reporting is in conflict with the definition of the wor&