Reading numbers: Per capita

Divide the growth by the people.

The economy is a total; people are the denominator. Both grow. Per capita is what remains after the second growth eats part of the first, and it is the honest way to ask whether a bigger economy means better-off Indians.

Concept Per capitaIllustrated with A worked exampleSource MoSPI, NSOLevel First principlesReading time 5 min

A total, divided

First principles

India's economy can grow at 8 per cent while the average Indian's share grows more slowly. Both things are true at once, and no trick is involved. The total grows. The population grows too. Per capita is what is left after the second growth eats part of the first.

The phrase does one job superbly: it lets you compare economies of different sizes, and one economy with its own past. India's total GDP dwarfs Sri Lanka's and always will; per head, the comparison becomes a real question. Likewise across time: the economy is many times larger than it was in 1991, and the meaningful part of that claim is the growth per person.

The arithmetic, with toy numbers

A worked example, illustration, not data

GDP growth, toy economy

+8%

the total, one year on

Population growth, toy economy

+1%

the denominator grows too

Per capita growth

≈ +7%

what each share did

The exact figure

6.9%

1.08 ÷ 1.01, minus one

Imagine a toy economy of ₹100 shared among 100 people: ₹1 per head. A year later the economy is ₹108 and the people are 101. The total grew 8 per cent, but the share per head grew to about ₹1.07, a gain of roughly 7 per cent. The exact answer is 1.08 divided by 1.01, which is 6.9 per cent. The missing point and a bit was population, doing quiet arithmetic on the headline.

Over a decade the discount compounds. A country can double its economy while less than doubling the means of its people, and the gap between those two sentences is exactly population growth. This is not an argument that growth fails; it is a reminder that the headline and the household are connected by a denominator.

What the average cannot say

A limit, stated plainly

Per capita is an honest answer to a narrow question: how much is there, per person, on paper? It cannot answer who got the growth. If one person's income doubles and everyone else's stands still, the average rises while four people out of five feel nothing. Whether growth reached the median Indian is a question about distribution, and it needs a different tool. That is the subject of the companion note on averages and distribution.

Used well, per capita is the right way to compare countries of different sizes, or a country with its own past. Used badly, it is a total wearing an individual's clothes. The economy is bigger. Whether people are better off is a separate claim, and it stands on separate evidence.

How to misread this concept

i.

“8 per cent growth means 8 per cent for me.”

No. It means the total grew 8 per cent. Your share depends on population growth first and on distribution after that. The headline is a statement about the economy, not about you.
ii.

“A bigger economy is always a richer people.”

Not by itself. If population grows as fast as output, per capita stands still while the total doubles. Size and prosperity are different axes, and a country can move along one without moving along the other.
iii.

“Per capita is the typical person's income.”

No: it is the average, and the average is nobody. The typical person is the median, who can sit far below the mean when income is concentrated at the top. The two are different instruments for different questions.