How Many People There Are

In one line

India is the most populous country in the world, its population is still growing although its fertility has fallen to about replacement level, and the growth now comes from the age structure rather than from the birth rate.

In the wording a student can write in an exam: India's population is enumerated by the decennial census, conducted under the Census Act 1948, and estimated between censuses by the Sample Registration System and by official projections. The total fertility rate, being the average number of children a woman would bear over her lifetime at current rates, has fallen to about the replacement level of 2.1, and yet the population continues to grow because of population momentum, which is the effect of a very large cohort of people already in their reproductive years.

The sources, which matter more than the numbers

MU's 2022 paper says "According to United Nations data India is the World's populous nation", so the examiner herself cites a source. A candidate should do the same, and should name four.

The census. Conducted decennially under the Census Act 1948, and the basis of every official figure on population, literacy, household amenities, migration and urbanisation. A candidate should note that the census due in 2021 was postponed, so the most recent complete enumeration is of 2011, and every figure for the years since is an estimate or a projection.

The Sample Registration System. A continuous demographic survey run by the Registrar General, which is the source for birth rates, death rates, infant mortality and the total fertility rate between censuses.

The National Family Health Survey. A large sample survey which is the source for fertility, contraceptive use, nutrition and health indicators by State and by social group.

United Nations population estimates and projections. The source of the international comparison, and the basis for the widely reported estimate that India became the most populous country.

The discipline to observe. Give the source and the order of magnitude. "The total fertility rate has fallen to about the replacement level, on the National Family Health Survey" is worth more than a decimal figure quoted from a textbook printed some years ago, and it cannot be wrong in the way the decimal can.

The four facts that carry an answer

India is the most populous country in the world. MU's own paper says so, citing United Nations data.

The rate of growth has fallen substantially. The decadal growth rate recorded by successive censuses has been declining for several decades, and the total fertility rate has fallen from well above replacement to about replacement level.

The population is nevertheless still growing, and will continue to grow for some decades. This is population momentum, and it is the fact most often misunderstood. Even if every couple from today had exactly two children, the population would continue to rise for a generation, because the number of couples is itself very large: a large cohort born when fertility was high is now of reproductive age.