World Population Growth
A population may increase or decrease over time. This change depends on the birth rate, death rate and migration. A population grows if the birth rate is greater than the death rate (a natural increase). In some countries the death rate is greater than the birth rate which results in natural decrease. Migration can also have a significant impact on population.
Lecture on population growth over human history.
Video – population change and structure
Factors affecting birth rates
Birth rate – the number of babies born per year for every 1000 people.
Higher birth rates Lower birth rates
- Lack of access to contraception: LEDCs tend to have poor access to contraception which results in higher birth rates.
- Early marriage: early marriage in LEDCs leads to higher birth rates as women have more time to have children .
- Carrying on family name: boys are prized in many cultures to carry on the family name, families will continue to have children until they have a boy resulting in higher birth rates.
- Traditional role of women: in many LEDCs women are viewed as homemakers and their role is to look after children.
- Polygamy: in some cultures e.g. Bedouin tribe multiple marriages can result in higher birth rates
- Workers: more children mean more workers so poorer families have more children to work, support themselves in their old age or to work on the farm
- High infant mortality: poor sanitation and medical care mean that many infants die young so people have more children to compensate.
- Status: in some countries e.g. Kenya the larger the family, the stronger the man(!) resulting in higher birth rates.
- Religion: high birth rates as the use of contraception is banned e.g. Catholicism which raises birth rates.
- Availability of contraception: couples can decide whether or not to have children which decreases the birth rate
- Sex education: people are more aware of contrapcetion methods etc which lowers the birth rate
- Population control strategies: some countries e.g. China restrict birth which lower the birth rate.
- Career women: in MEDCs many women now work and delay having children thus lowering the birth rate.
- Finances: some couples decide the limit their family to one or two children as the cost of bringing them up is expensive.
- Cultural norms: one or two children is seen as a ‘normal’ family size.
Factors affecting death rates
Death rate – the number of deaths per 
year per 1000 people.
- Access to healthcare
- Natural disasters e.g. earthquakes, floods
- Diseases e.g. HIV/AIDs
- Human-induced illnesses e.g. obseity, lung cancer (due to smoking)
- War
- Access to clean water and sanitation
- Famine
Demographic Transition Model
Population Pyramids
A population pyramid is a graph that tells you about the age and gender structure of a population. Different shapes of the population pyramids can tell us different things about a population e.g. birth rates, death rates and life expectancy.
BBC Bitesize – population pyramids
Want to know how population pyramids vary from country to country and over time? Use this website to pick the year and country you want then see it build the population pyramid.