Human Population Models (SL IB Environmental Systems & Societies (ESS))

• Age–gender pyramids and demographic transition models (DTM) can be useful in the prediction of human population growth

Demographic Transition Model

• The DTM is a model that shows how a population transitions from a pre-industrial stage with high crude birth rates and high crude death rates to an economically advanced stage with low or declining crude birth rates and low crude death rates
  • The demographic transition model illustrates five generalised stages that countries pass through as they develop
  • It shows how the birth and death rates change and how this affects the overall population as the country

The Demographic Transition Model

Stage 1

• • The total population is low 
  • High birth rates due to lack of contraception/family planning 
  • High death rates due to poor healthcare, poor diet and famine
  • High infant mortality which leads people to have more children so that some children survive to adulthood

Stage 2

• • The total population starts to rise rapidly
  • Birth rates remain high as people continue to have large families
  • Death rates decrease as a result of improved diets, better healthcare, lower infant mortality and increased access to clean water

Stage 3

• • The total population continues to increase but the rate of growth begins to slow
  • Birth rate begins to fall rapidly due to increased birth control, family planning, increased cost of raising children and low infant mortality rate 
  • Death rate still decreasing but at a slower rate as improvements in medicine, hygiene, diet and water quality continue

Stage 4

• • The total population is high and is increasing slowly 
  • Birth rate is low and fluctuating due to accessible birth control and the choice of having fewer children as well as delaying the age women start to have children
  • Death rate is low and fluctuating

Stage 5

• • The total population starts to slowly decline as the death rate exceeds the birth rate 
  • Birth rate is low and slowly decreasing
  • Death rate is low and fluctuating

Population Pyramids

• A population pyramid (also known as an age–gender pyramid) is a graphical representation of a population's age and gender structure
  • It displays the percentage or number of individuals in each age group and gender within a given population, typically a country or region

• The population pyramid is usually represented as a horizontal bar graph, with the age groups displayed along the vertical axis, and the percentage or number of individuals in each age group displayed along the horizontal axis
  • The left side of the graph displays the male population, while the right side shows the female population

• The shape of the population pyramid can provide insights into the demographic characteristics of a population
  • For instance, a pyramid with a broad base and a narrow top indicates a young population with high fertility rates and low life expectancy, while a pyramid with a narrow base and a broad top indicates an aging population with low fertility rates and high life expectancy

An example of a population pyramid

• Population pyramids are widely used by demographers, economists, and policymakers to understand population trends, forecast future population growth, and plan for social and economic policies

• They are also used in fields such as public health, education, and social welfare to plan for the needs of specific age groups within a population
  • This means that governments can estimate and plan for spending

• As countries develop and pass through the stages of demographic transition the shape of the population pyramid changes 
• The population pyramid can be used to identify the following groups:
  • Young dependents 
  • Old dependents 
  • Economically active (working population)
  • Dependency ratio 

Population pyramid for Niger

• LEDCs like Niger typically have a concave pyramid shape
• At the start of stage 2 of the demographic transition model
• This indicates:
  • High birth rate
  • Low life expectancy
  • High death rate but starting to decrease
  • High infant mortality rate
  • Young dependent population dominates

Population pyramid for Nepal

• LEDCs/NICs (newly industrialised countries) that are a little further along the demographic transition, such as Nepal, typically have a pyramid shape
• Stage 3 of the demographic transition model
• This indicates:
  • Decreasing birth rate 
  • Increasing life expectancy
  • Decreasing death rate
  • Decreasing infant mortality
  • Larger working age population

Population pyramid for USA

• HICs (high income countries) such as the USA typically have a column shape
• Stage 4 of the demographic transition model
• This indicates:
  • Decreasing birth rate 
  • Increasing life expectancy
  • Decreasing death rate 
  • Low infant mortality
  • Larger working age population

Population pyramid for Japan

• HICs such as Japan then start to develop a pentagon shape with a narrowing base
• Stage 5 of the demographic transition model
• This indicates:
  • Decreasing birth rate 
  • Increasing life expectancy
  • Death rate is higher than the birth rate due to the ageing population
  • Low infant mortality
  • Ageing population - older dependent population

Implications of population structure

• Population pyramids mean that population issues can be identified
• There are range of issues including: 
  • Ageing populations
  • Falling birth rates 
  • Impacts of migration

Ageing Populations

• Many HICs are experiencing ageing populations and an increase in the older dependent population
• The implications of this include:
  • Increased number of pension payments
  • Increased need for care homes
  • Increased pressure on the healthcare service and social care
• It also results in fewer workers which means:
  • Governments are not able to collect as much tax
  • Some areas suffer worker shortages

Falling birth rates

• Countries experiencing falling birth rates include many HICs and MICs (middle income countries)
• The implications of this include:
  • School closures due to fewer children
  • Future workforce shortages 

Migration

• In some countries migration can lead to an imbalance in the population structure
• The UAE has significantly more males than females 
• 29% of the population are males between the ages of 25 and 39 whereas only 10.5% of the population are women 25-39
• This is the result of the migration of males to the UAE to work in the oil, gas and construction industries
• Rapid population growth in some areas as a result of migration can lead to:
  • Increased pressure on services such as healthcare and schools
  • A shortage of housing
  • Increased traffic congestion
  • Increased water and air pollution
  • Shortage of food
  • Lack of clean water