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First teaching 2015

Last exams 2025

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

Revision Note

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Alistair Marjot

Written by: Alistair Marjot

Reviewed by: Bridgette Barrett

Human Population Models

  • 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

demographic-transition

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

population-structure-2

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-niger

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---nepal

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---usa

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---japan

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

Worked Example

A population pyramid is shown below.

What does the shape of the pyramid tell you about the population structure of the country?

5YVJ9dns_population-pyramid-italy-worked-example

Answer

  • The narrow base means a low birth rate

  • A low birth rate means a low number of young dependents

  • A reasonably broad top means high life expectancy

  • The majority of the population is between 40 and 60

  • This means there will be a large number of elderly dependents in the future

Worked Example

The figure below shows population pyramids for Mexico in 1980 and 2010.

Describe the changes in Mexico's population structure between 1980 and 2010.

002acb54-af1b-48cb-8a3b-4451f2bcaf32

Answer

  • In 2010 there are:

    • More economically active / working / 15-64 year-olds

    • More elderly / old dependents / 65+ year-olds

    • More young dependents in total / bands up to 19 become more even

Examiner Tips and Tricks

Remember - when interpreting a population pyramid you need to look at four key areas:

  • Younger population - is the birth rate high or low?

  • Working population - are there enough people of working age to support the young and old dependents?

  • Elderly population - is it large or small? (if it is large, then life expectancy is high)

  • Male/female split - are there any noticeable differences between the numbers of males and females?

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Alistair Marjot

Author: Alistair Marjot

Expertise: Biology & Environmental Systems and Societies

Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

Bridgette Barrett

Author: Bridgette Barrett

Expertise: Geography Lead

After graduating with a degree in Geography, Bridgette completed a PGCE over 25 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.