Totals versus "per person"

By the end of this lesson you can explain why a big country can have the biggest total but not the biggest rate.

Why it matters

"Most cases are in the capital city!" That is not surprising: it is where lots of people live. Comparing totals between places of very different sizes often just tells you which place is bigger. Rates fix that, and they can turn a story upside down.

The idea in plain words

Imagine two families sharing pots of rice. Family A has 12 people and cooks 6 kg. Family B has 2 people and cooks 2 kg. Family A cooked more rice in total. But per person, Family A ate 6 ÷ 12 = 0.5 kg each, and Family B ate 2 ÷ 2 = 1 kg each. Family B ate twice as much each.

Total: the whole amount for a place or group.

Per person (per capita): the total shared out equally between everyone: total ÷ number of people. It is one kind of rate.

Rate: an amount compared with the size of the group, so that groups of different sizes can be compared fairly.

Here are the real carbon dioxide (CO₂) totals for our 17 countries in 2024.

Totals. China gives off by far the most CO₂. Qatar (amber) is 14th of 17.

See it done

Data: country-indicators.csv (real). Column E is population; column F is co2_million_tonnes.

Question: which country gave off the most CO₂ per person in 2024?

1. Plan. Per person = total ÷ people. The total is in million tonnes, so first multiply by 1,000,000 to get tonnes.
2. Make a new column. In G1 type co2_per_person_t. In G2 type =ROUND(F2*1000000/E2,1) and press Enter. (Without ROUND, the cell would show many decimal places, such as 41.27109406. ROUND(...,1) keeps one decimal place.)
3. Copy it down. Copy G2, select G3 to G596, and paste. Each row now has its own CO₂ per person, in tonnes.
4. Keep only 2024. Data, Create a filter, then filter year to 2024. 17 rows show.
5. Sort by the new column, biggest first. Click the filter button in G1 and choose Sort Z → A. The 17 rows showing are now in order, biggest first.
6. Read the top. Qatar: 41.3 tonnes per person. Then Australia 14.5, the United States 14.2, and China 8.7 (fourth).

The new column G shares each total out between everyone.

Per person. Qatar jumps from 14th to 1st. China drops from 1st to 4th.

7. Put the sheet back. Press Ctrl + Z (⌘ + Z on a Mac) to undo the sort, then Data, Remove filter. The rows return to their original order (by country, then year), which lesson 5.3 needs.
8. Say both stories. "In 2024, China gave off the most CO₂ in total (12,289.0 million tonnes), but Qatar gave off the most per person (41.3 tonnes for each person, compared with China's 8.7)."

Your turn, with help

Nigeria's 2024 total (135.8 million tonnes) is bigger than Qatar's (125.8 million tonnes). Use your column G: what is each country's CO₂ per person?

Hint: Nigeria has about 233 million people; Qatar about 3 million. Which do you expect to be higher per person?

Show the answer

Nigeria 0.6 tonnes per person; Qatar 41.3. Nigeria's total is a little bigger, but it is shared between far more people. Per person, Qatar's is about 70 times Nigeria's (41.3 ÷ 0.6 is about 69, using the rounded values).

Your turn, alone

1. Which country was 3rd largest in total CO₂ in 2024, and where does it rank per person?
2. Which country had the lowest CO₂ per person in 2024?
3. Amara sells 103 oranges in 13 sales and 22 watermelons in 13 sales. What is the average number of each fruit per sale? (Round to one decimal place.)
4. A news story says, "Lagos has more road accidents than any other Nigerian city." What extra number would you ask for?

Check your answers

1. India: 3rd in total (3,193.5 million tonnes), but 2.2 tonnes per person, 13th of the 17.
2. Kenya, 0.4 tonnes per person.
3. Oranges: 103 ÷ 13 = 7.9 per sale. Watermelons: 22 ÷ 13 = 1.7 per sale.
4. How many people (or cars, or trips) there are in each city, so you can compare accidents per person (or per trip). Lagos is very large, so a large total is expected.

Watch out

• Comparing totals between places of different sizes. Ask: "per person?" (or per pupil, per car, per day).
• Forgetting the units. Million tonnes is not tonnes. Convert before dividing, or the answer is a million times too small.
• Rates for tiny groups. A town of 50 people with 1 case has a rate of 1 in 50. One more case doubles it. With small groups, rates jump around a lot.

Say it back

1. How do you work out a per-person figure?
2. Which country had the most CO₂ in total in 2024, and which per person?
3. Why can a big country top the totals but not the rates?

Show the answers

1. Total ÷ number of people.
2. China in total; Qatar per person.
3. Its total is shared between many more people.

What is next

Japan's CO₂ "shot up" between 2009 and 2013. That is true. So is the opposite story. It all depends on which years you choose to show. Next lesson.

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Data in this lesson: Global Carbon Budget (2025); UN World Population Prospects (2024), processed by Our World in Data. Licensed under CC BY 4.0 (UN data: CC BY 3.0 IGO). Extract and continent labels by DataMedics.