Population Growth: Effects and Control

25 min

Let's begin

In 1978 a Rwandan woman had, on average, 8.6 children; by 2022 the figure was 3.6 (NISR). Over the same years the crude death rate fell from 17.1 to 6.3 deaths per 1,000 people. Both changes matter, and the gap between them is what drives growth. Across Africa the same story, at different speeds, took the continent from about 228 million people in 1950 to about 1.48 billion in 2023 (Figure 3).

Definition

Crude birth rate (CBR): live births per 1,000 people in a year. Crude death rate (CDR): deaths per 1,000 people in a year. Rate of natural increase: $\text{natural increase (\%)} = \frac{\text{CBR} - \text{CDR}}{10}$ Total fertility rate (TFR): the average number of children a woman would have in her lifetime at current rates.

Figure 3: Africa's population, 1950–2023.

Rwanda's demographic indicators (NISR, 2022 census)

Indicator	Earlier	2022
Total fertility rate (children per woman)	8.6 (1978); 6.9 (1991); 5.9 (2002)	3.6
Crude birth rate (per 1,000)		27.8
Crude death rate (per 1,000)	17.1 (1978)	6.3
Infant mortality (per 1,000 live births)	49 (2012)	28.9
Life expectancy at birth (years)	46 (1978); 64 (2012)	69.6 (men 67.7, women 71.2)
Annual growth rate, 2012–22		2.3%

Why Africa's population grows fast

Birth rates are still high: early marriage; children valued as farm labour and as security in old age; low use of family planning in many areas; fewer years of schooling for girls; cultural and religious attitudes to large families.
Death rates have fallen: vaccination, clean water, better nutrition and health care save many more children than in 1950.
A young structure: so many young people are entering their child-bearing years that the population keeps growing even as each woman has fewer children (population momentum).

Effects of rapid growth

Positive	Negative
A large, young labour force	Pressure on land: plots shrink as they are divided among children; soils are over-used
A bigger market for goods and services	Unemployment and under-employment among the young
More ideas, enterprise and skills	Overcrowded schools, clinics and housing; high dependency ratio
Cheap labour can attract investment	Deforestation, soil erosion and shortages of fuelwood and water

Controlling growth

Family planning services, available and affordable, with accurate information.
Education for girls: NISR (2022) finds the lowest fertility among women with secondary education or above (3.4 children per woman).
Better child survival, so parents do not need many births to be sure some children survive.
Jobs for women, later marriage, and pensions and savings schemes, so old-age security does not depend on many children.
Public awareness campaigns through health centres, schools and community meetings.

Kurzgesagt – In a Nutshell: Overpopulation & Africa. Watch for the 'demographic transition': why falling death rates come first and birth rates follow, and what makes birth rates fall.

Worked example

Worked example 1: natural increase. In 2022 Rwanda's crude birth rate was 27.8 per 1,000 and its crude death rate 6.3 per 1,000 (NISR). Calculate the rate of natural increase.

$27.8 - 6.3 = 21.5$ per 1,000.
$\frac{21.5}{10} = 2.15\%$ per year.
This is close to the census growth rate of 2.3% per year for 2012–22; the two differ because the census rate also reflects migration and the way it is averaged over ten years.

Worked example

Worked example 2: doubling time. A quick rule says a population growing at $r %$ a year doubles in about $\frac{70}{r}$ years. How long would Rwanda take to double at 2.3%?

$\frac{70}{2.3} \approx 30$ years.
So at that rate the 13.2 million of 2022 would be about 26 million by the early 2050s.
In practice the rate is falling as fertility falls, so doubling would take longer.

Warning

Falling fertility does not stop growth at once. Because Rwanda's pyramid has such a wide base, there are more young women each year, so births can stay high even when each woman has fewer children. Do not write "TFR has fallen, so the population has stopped growing".

Tip

Growth = births − deaths ± migration. For any country, ask which of the three changed, then why.

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Practice

Define crude birth rate and total fertility rate.
Using Figure 3, estimate how many times Africa's population grew between 1950 and 2023.
Give three reasons why birth rates remain high in many African countries.
Give two positive and two negative effects of rapid population growth.
Calculate the fall in Rwanda's TFR between 1978 and 2022, and express it as a percentage of the 1978 value.
Explain how improved child survival can help to reduce birth rates.
Assess the importance of girls' education as a measure to control population growth.

Show answersHide answers

CBR: live births per 1,000 people per year. TFR: average number of children a woman would have in her lifetime at current rates.
$1{,}480.8 \div 227.8 \approx 6.5$ times.
Any three: early marriage; children valued for labour and old-age security; limited use of family planning; fewer years of schooling for girls; cultural or religious preference for large families.
Positive: large labour force; bigger market (or enterprise, investment). Negative: pressure on land; unemployment; overcrowded services; environmental damage.
$8.6 - 3.6 = 5.0$ children; $\frac{5.0}{8.6} \times 100 \approx 58\%$ .
When fewer children die, parents can be confident that their children will survive, so they choose to have fewer births.
Educated women tend to marry later, know about and use family planning, work outside the home and choose smaller families; NISR finds the lowest TFR (3.4) among women with secondary education. But in Rwanda the difference by education is small (3.4 to 3.9), so education works best alongside health services, child survival and jobs. A good answer calls it important but not sufficient alone.

Sources and credits

National Institute of Statistics of Rwanda (NISR), Fifth Rwanda Population and Housing Census 2022, Main Indicators Report: executive summary and Figures 8, 9 and 12–14 (births, deaths, fertility, life expectancy, child mortality); Table 4 (growth rate). Figures used as published.
Population of Africa, 1950–2023: Population, Our World in Data, based on UN World Population Prospects 2024, CC BY 4.0. Chart drawn by Ganzaa from the data.
Video: Overpopulation & Africa, Kurzgesagt – In a Nutshell, embedded from YouTube.
Explanations, worked examples and exercises: written by Ganzaa.

1Rwanda's demographic indicators (NISR, 2022 census)

2Why Africa's population grows fast

3Effects of rapid growth

4Controlling growth

Rwanda's demographic indicators (NISR, 2022 census)

Why Africa's population grows fast

Effects of rapid growth

Controlling growth