Population Growth Facts
- For most of human history population growth was negligible due to high mortality (especially among children) despite high fertility rates.
- Rapid population growth dates back to the late 18th and 19th Centuries due to introduction of basic healthcare and improved living conditions in future HICs.
- The world population has reached 8 billion and is expected to stabilize by the end of 21st Century at between 10 to 12 billion. By 2100-2150 it could be down to 9 billion.
- In 2023 India has overtaken China as the most populated country in the world
- About 10% of world’s population is over 65 - by 2100 this proportion will have risen to one-third
- The average total fertility rate dropped significantly from 5.06 in 1964 to 3.28 in 1990 and then further to 2.3 currently.
- Now Over 50% of the world's population can be found in Asia, but its share in global population will decline whereas Africa's will increase.
- Population growth in Asia will be over by the mid-21st Century, whereas Africa is the only region projected to experience further population growth throughout the 21st Century.
Trends in Fertility, Mortality, and Dependency
Natural Increase: The Balance Between Births and Deaths
Natural increase
Natural increase is the difference between the crude birth rate (CBR) and the crude death rate (CDR), expressed as a percentage.
Calculating Natural Increase
- Crude Birth Rate (CBR): Number of live births per 1,000 people per year.
- Crude Death Rate (CDR): Number of deaths per 1,000 people per year.
$$\text{Natural Increase (%) = CBR - CDR}$$
Fertility Rate: The Drivers of Population Growth
Total Fertility Rate (TFR)
The total fertility rate (TFR) is the average number of children a woman is expected to have during her reproductive years (ages 15–49), also called childbearing age.
The TFR of 2.1 is called a replacement rate - rate that allows to maintain the same population size over time.
Influencing Factors
- Status of Women: Higher education and employment opportunities often lead to lower fertility rates.
- Economic Conditions: In LICs, children may be seen as economic assets, increasing fertility rates.
- Cultural and Religious Norms: Some societies encourage larger families.
- Access to Healthcare: Availability of contraception and maternal health services can reduce fertility rates.
Japan has high female employment rates but low fertility (1.2) due to the high cost of childcare and cultural work-life balance challenges.
ExampleNigeria's fertility rate remains high (5.2 children per woman) due to reliance on agriculture and limited access to contraception.
Dependency Ratio: Balancing the Working and Non-Working Populations
Dependency ratio
- The dependency ratio measures the proportion of dependents (people aged below 15 and above 65) to the working-age (economically active) population (15–64).
- Older dependency ratio measures the proportion of old dependents (people aged above 65) to the working-age (economically active) population (15–64).
Calculating Dependency Ratio
$$\text{Dependency Ratio} = \frac{\text{Number of Dependents}}{\text{Working-Age Population}} \times 100%$$
- Don't confuse the dependency ratio with the proportion of elderly people.
- Remember, the dependency ratio includes both the young and the elderly.
- While the dependency ratio is a useful indicator, it is a crude measure.
- Many people work beyond age 64 or remain in education past age 15.
Key Demographic Metrics
Infant Mortality Rate (IMR)
Number of deaths of children under 1 year per 1,000 live births.
Child Mortality Rate (CMR)
Number of deaths of children under 5 years per 1,000 live births.
Life Expectancy
Average number of years a person is expected to live based on current mortality rates.
- Life expectancy varies widely across the world.
- In HICs, it exceeds 80 years.
- In LDCs, it ranges between 50 and 55 years.
Women Generally Live Longer Than Men
- Factors include lower retirement ages, reduced physical labor, and lower participation in physically dangerous jobs (e.g. mining, construction).
- Less direct involvement in conflict and significantly lower participation in organized crime and interpersonal violence.
- Men are also more likely to engage in “self-destructive” and risky behaviors like excessive smoking and drinking.
In some countries, life expectancy can be declining due to poverty, conflict (e.g. South Sudan, Syria), and diseases like AIDS (e.g. Botswana in the 1990s).
TipDon't assume that a longer life expectancy equates to a higher quality of life. Many elderly individuals face health challenges, poor living conditions, and social isolation.
Population Growth Can Continue Despite Falling Fertility Rates
Population momentum
Population momentum refers to the continued population growth despite falling fertility rates below replacement rate (2.1).
- This occurs when a large proportion of the population is in their childbearing years, leading to higher absolute numbers of births even with lower fertility rates.
The Demographic Transition Model Describes Population Change In Stages
- Imagine two countries: Japan and Nigeria.
- Japan faces an aging population with a shrinking workforce.
- Nigeria grapples with rapid population growth and a youthful demographic.
- These contrasting scenarios reflect the stages of the Demographic Transition Model (DTM) and illustrate how trends in fertility, mortality, and dependency shape societies over time.
Demographic Transition Model (DTM)
The demographic transition model (DTM) is a theoretical framework that describes population change over time through distinct stages of development. It examines the relationship between birth rates, death rates, and overall population growth as a country develops economically and socially.
