Trends in world population growth

Detail

1. How fast human numbers have grown

• Human numbers grew more than 10 times in the last 500 years.
• They grew about 4 times in the 20th century alone.
• At the start of the 21st century, the world had over 6 billion people (NCERT).
• In 1798, Thomas Malthus argued that population grows faster than food supply. The two centuries after him tested that idea. Food supply kept up, mainly because farming became far more productive.
• World population growth trend means the long-run path of world population size over time. For most of history the line was almost flat. After about 1750 it rose very steeply.

2. Milestones: each new billion

Milestone here means the year world population first reached a given billion (UN estimates).

Billion	Year reached	Years taken from previous billion
1st	~1804	all of human history
2nd	1927	~123
3rd	1960	33
4th	1974	14
5th	1987	13
6th	1999	12
7th	2011	12
8th	15 November 2022	~12 [4]
9th (projected)	~2037	~15 [4]

• World population of 8 billion: the UN marked 15 November 2022 as the "Day of Eight Billion", the day it estimated world population reached 8 billion [4][5].
• Going from 7 to 8 billion took 12 years. Going from 8 to 9 billion should take about 15 years (to 2037). This shows the overall growth rate is slowing [4].
• Where the 8th billion came from:
• About half came from Asia [5].
• Africa gave the second-largest share, almost 400 million [5].

• 10 countries added more than half of the growth. India added by far the most, then China and Nigeria [5].

• In April 2023, India overtook China as the world's most populous country [7].

3. Why numbers surged after 1750

The main cause was simple: deaths fell long before births fell.

• Agricultural and industrial revolutions → more food was grown, and railways and steamships could carry it → fewer famines.
• Vaccination and sanitation (clean water, sewers) → fewer deaths from smallpox, cholera and other diseases.
• Then, in the 20th century, antibiotics and the Green Revolution (high-yielding seeds, fertiliser and irrigation from the 1960s) → death rates fell sharply in Asia, Africa and Latin America.
• Result: birth rates stayed high while death rates dropped, so the gap between births and deaths (the natural increase) widened, and population grew very fast.
• The UN gives the same reasons: people live longer because of better public health, nutrition, personal hygiene and medicine. Fertility (the average number of children born per woman) has also stayed high in some countries [4].
• This sequence is the basis of the demographic transition model. It describes how a country moves from high birth and death rates, through falling death rates, to low birth and death rates.

4. Spatial pattern of growth: who is growing, who is shrinking

• Africa has the highest growth rate of all the continents (NCERT exercise).
• Sub-Saharan Africa (Africa south of the Sahara Desert) will supply more than half of world growth to 2050.
• Eight countries will account for over half of the projected increase to 2050 (UN WPP 2022): Democratic Republic of the Congo, Egypt, Ethiopia, India, Nigeria, Pakistan, the Philippines and Tanzania.
• Europe and East Asia are shrinking.

Group (WPP 2024)	Number of countries	Examples
Population already peaked before 2024	63 (28% of world population in 2024)	China, Germany, Japan, Russian Federation [2][3]
Peak expected between 2025 and 2054	48	Brazil, Iran, Turkey, Vietnam [2]
Still growing after 2054	126	India, Indonesia, Nigeria, Pakistan, USA [2]

• In the group that has already peaked, population is expected to fall by 14% over the next 30 years [2].
• Some countries will grow very fast. Their populations are expected to double between 2024 and 2054, for example Angola, Central African Republic, DR Congo, Niger and Somalia [2].
• Fertility: women today have one child fewer, on average, than around 1990 [2].
• Nearly one-fifth of all countries now have ultra-low fertility: fewer than 1.4 births per woman [2].
• Replacement level fertility is about 2.1 births per woman. At this level each generation just replaces itself [2].

5. Projections: World Population Prospects (WPP)

• The World Population Prospects is the UN's official set of population estimates and projections for every country. It is published by the UN DESA Population Division (UN Department of Economic and Social Affairs), usually every two years.
• WPP 2024 headline figures:
• 8.2 billion in 2024 [2]
• Peak of about 10.3 billion in the mid-2080s [2][3]

• About 10.2 billion by 2100 [2]

• These figures are 700 million (6%) lower than the forecast made a decade earlier [2]. The 2022 projection had put the peak at about 10.4 billion in the 2080s [4].

• WPP 2024 puts the chance that world population peaks within this century at 80%. In the 2013 projections this chance was only about 30% [3].
• India: expected to keep growing and to peak in the early 2060s at about 1.7 billion.
• China: its population has already peaked and is now declining [2][3].
• Ageing:
• Global life expectancy reached 73.3 years in 2024, back above the pre-COVID level of 70.9 years [2].
• By the mid-2030s, people aged 80 and over will outnumber infants (children under 1) [3].
• By the late 2070s, people aged 65 and over will outnumber children under 18 [3].

6. Population momentum

• Population momentum means that population keeps growing for decades even after fertility falls to replacement level (about 2.1). This happens when a population has a young age structure (how the population is divided among age groups).
• How it works:
• Past high fertility → a large share of young people.
• These young people enter child-bearing ages → even if each couple has only about 2 children, the number of couples is very large.

• Births stay above deaths for decades → population keeps rising.

• Where it is seen: India and much of South Asia. Most of India's growth, and of the world's growth to 2050, comes from momentum, not from high fertility.

• In the opposite direction, Japan and much of Europe have negative momentum. Few young people means population keeps falling even if fertility rises.

7. The rights angle: UNFPA State of World Population report

• The State of World Population (SWOP) report is the annual flagship report of UNFPA (UN Population Fund).
• 2025 edition: "The Real Fertility Crisis: The Pursuit of Reproductive Agency in a Changing World" [6].
• Main argument: the real crisis is not too many or too few people. It is a lack of reproductive agency: people's freedom and ability to choose whether, when and how many children to have [6].
• 1 in 5 people expect not to have the number of children they want [6].
• More than half named economic barriers, such as the cost of parenthood, job insecurity and housing [6].
• Other reasons were fear about the state of the world and not having a suitable partner [6].
• 1 in 5 said they had been pressured to have children, and 1 in 3 adults have had an unintended pregnancy [6].

8. Impact of population change

Rapid growth (e.g. Sahel, sub-Saharan Africa, parts of South Asia)	Slow or negative growth (e.g. Japan, Italy, East Asia)
Pressure on food, water, housing and jobs	Labour shortages
Overcrowded cities and slums	Heavy pension and old-age care costs
Forest loss, soil degradation, groundwater stress	Empty villages: Japan's akiya (abandoned homes); Italy's one-euro houses sold to attract new residents
A demographic dividend if the young get jobs and skills	Shrinking tax base and school closures

• Link to climate change: greenhouse-gas emissions depend more on consumption than on headcount. A high-income person emits far more than a person in a fast-growing low-income country.
• Link to human development: falling fertility usually follows better girls' education, health care and incomes.

Prelims Hooks

• The UN's "Day of Eight Billion" was 15 November 2022. Going from 7 to 8 billion took 12 years. The 9th billion is expected around 2037, after about 15 years [4].
• Correct order of the billion milestones: 1804 → 1927 → 1960 → 1974 → 1987 → 1999 → 2011 → 2022.
• WPP 2024: 8.2 billion in 2024 → peak of ~10.3 billion in the mid-2080s → ~10.2 billion by 2100 [2].
• WPP is published by UN DESA. SWOP is published by UNFPA. A common trap is to swap the two.
• SWOP 2025 theme: "The Real Fertility Crisis". It is about reproductive agency, not overpopulation [6].
• China, Germany, Japan and Russia are among the 63 countries whose population peaked before 2024. India is still growing [2].
• India became the most populous country in April 2023, overtaking China [7].
• Replacement level fertility is about 2.1. Population that keeps growing after fertility falls to this level is due to population momentum.
• Africa has the highest population growth rate of all the continents (NCERT).

Mains Points

• Causes of the post-1750 surge:
• The agricultural and industrial revolutions, vaccination, sanitation, antibiotics and the Green Revolution cut death rates.
• Birth rates fell only later. This lag, explained by the demographic transition model, produced very fast growth.

• World population grew about 4 times in the 20th century.

• Changing spatial pattern:

• Growth is now concentrated in sub-Saharan Africa and South Asia.
• Europe, East Asia and Russia are shrinking.
• 63 countries have already peaked (WPP 2024) [2].

• This creates two opposite policy problems: jobs and services for the young, and pensions and care for the old.

• Policy lesson from momentum and agency:

• India's future growth comes mainly from momentum, not high fertility. So coercive population control is unnecessary.
• Investment in health, education and jobs to use the demographic dividend matters more.

• UNFPA's SWOP 2025 adds that the real goal is reproductive choice [6].

• Population and environment:

• Fast growth strains food, water and land.
• But climate impact depends on consumption more than numbers.
• So both population policy and sustainable consumption are needed, linking GS-I (population) with GS-III (environment).