Population Structure (DP IB Geography)

Revision Note

Population Pyramids

  • The characteristics of a population, the distribution of age, sex, ethnicity, religion etc, is known as the population structure

  • It is the result of changes in:

    • Fertility

    • Mortality

    • Migration

  • Two of these characteristics can be shown as an age-sex structure or population pyramid

  • This is a graphical illustration of the distribution of a given population, grouped by age and gender

  • It can be used to represent a population of any region, city, country or even the world

  • As the population grows the shape of the pyramid changes 

  • The population pyramid can be used to identify the following groups:

    • Young dependents 

    • Old dependents 

    • Economically active (working population)

    • Dependency ratio 

Features of a population pyramid

Population pyramid diagram showing age distribution between males (blue) and females (red) with annotations explaining birth rate, migration effects, and age longevity.
Generalised population pyramid
  • Population pyramids of places change over time

    • They show a place’s population structure at one point in time

    • The shape of the pyramid changes as a country moves through the stages of the demographic transition model

Chart showing demographic transition model with five stages: natural increase and decrease, birth and death rates on Y-axis, stages over time on X-axis, pyramid shapes for each stage with descriptions.
Population pyramids can be applied to the demographic transition model 
  • Population pyramids enable governments, nationally and regionally, to assess the needs of the population for services such as healthcare and education

  • This means the governments can estimate and plan for spending

Examiner Tips and Tricks

Although an exam question won’t directly ask you to draw a full pyramid, you may be asked to complete one from given data. Get used to annotating the main features, and shape of a population pyramid for any country. This is a useful exam technique, particularly if you are writing about population change in an essay, as it is an effective way of getting lots of points across in a short space of time.

Population pyramid of the USA

population-pyramid---usa
  • HIC countries such as the USA 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

Migration

  • In some countries, migration can lead to an imbalance in the population structure

  • The UAE has significantly more males than females 

    • In the UAE 29% of the population are males between the ages of 25 and 39 whereas only 10.5% of the population are women between 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

UAE population pyramid

uae-pop-pyramid

Japan's ageing population 

  • Japan's population fell from 128 million in 2007 to 125.8 million in 2020

  • The fertility rate is 1.36 births per woman which is well below the 2.1 fertility replacement rate

  • The birth rate is 6.8 per 1000

  • The death rate is 11.1 per 1000 

    • The death rate has increased from 6 per 1000 in 1979

    • This is not because healthcare or diets are worse but because there are far more elderly people who are more likely to become ill and die

  • Japan has the highest life expectancy in the world at 84.36 years

Japan from a pyramid to a column?

japan-pop-pyramid
  • By 2085, although the population of Japan will have shrunk overall, the pyramid shows a relatively stable population; one that isn’t growing or shrinking

  • The bars are about equal in all age groups, but become smaller at the top as people in the older age groups die

  • Populations with pyramids this shape have just about a replacement fertility and higher life expectancy 

Mexico's shrinking population

  • Mexico has a replacement fertility rate of just 1.8 (a TFR of 2.1 represents replacement level)

    • The reducing birth rate is due to out migration of young males

  • The median age in Mexico is 29.8 years

Mexico - from expanding to contracting

mexico-population-pyramid
  • From 1960 to 2022 the population of Mexico increased from 37.8 million to 127.5 million people - a growth of 237.6% in 62 years

  • The country represents 1.6% of the global population

  • Peak population growth occurred in 1965 at 3.34% and since then it has steadily declined. In 2022 population growth was just 0.63%

  • Median age has risen from a low of 15.1 years (1970) to 29.8 years (2022)

  • Life expectancy is 75 years - females 78.4 and males 71.8 years

  • Death rate decreased from 13 (1960) to 5 (2008) but increased to 7(2019) and further increased to 9.34/1000 in 2021, where it has remained

  • Infant mortality has declined from 159.6 per 1000 in 1950 to 10.5 per 1000 (2022)

  • Working age population stands at approximately 67%, however, by 2067 it is estimated it will be less than 60% with an ever increasing elderly population and decreasing young population

Examiner Tips and Tricks

When interpreting a population pyramid you need to look at four key areas 

  • Young dependents - is the birth rate high or low?

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

  • Old dependents - 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?

Dependency Ratio

  • Population structures and pyramids can be divided into three age-group categories, depending on the level of economic activity

    • Young dependents - from 0-14 years, they rely on their economically active parents to support them

    • Economically active - from 15-64 years, they are the working population who earn income, pay taxes and contribute to the support of the young and elderly

    • Elderly dependent - from 65 years onwards, they are no longer economically active and so rely on support from the state and younger family members

  • The amount that the young and elderly dependent population of a place depends on the economically active population can be measured 

    • This is expressed as the dependency ratio

bold italic d bold italic e bold italic p bold italic e bold italic n bold italic d bold italic e bold italic n bold italic c bold italic y bold space bold italic r bold italic a bold italic t bold italic i bold italic o bold space bold equals bold space fraction numerator bold young bold space bold dependents bold space bold plus bold space bold old bold space bold dependents over denominator bold working bold space bold population end fraction bold space bold cross times bold space bold 100

  • The higher the percentage of working-age people, the more income is being produced for a country to support those of non-working ages

  • An ageing population would have a high dependency ratio – as would a population with a very high birth rate

  • The dependency ratio tends to be:

    • Due to youthful population structure with many young dependents

      • In Niger the figure was 105 in 2021

      • This means for every 100 people of working age, 105 economically inactive young and elderly depend on them

    • Due to a large elderly dependent sector of the population

      • In Japan the figure was 57 in 2021

    • Due to few elderly dependents because previously there was low life expectancy

    • Also due to small number of young dependents because birth rates are falling

      • In Mexico the figure was 48 in 2021

    • Very high in LICs in stage 2 of the demographic transition model

    • High in advanced HICs in stage 4 and 5 of the demographic transition model

    • Lower in MICs in stage 3 of the demographic transition model

Examples of the Dependency Ratio

Country

% Young Dependents

% Elderly Dependents

% Economically Active

Dependency Ratio

Argentina

24.74

11.55

63.71

56.96%

Czech Republic

15.00

18.01

66.99

49.27%

Haiti

33.28

4.18

62.54

59.89%

India

28.09

5.95

65.96

51.60%

Madagascar

40.45

3.22

56.33

77.52%

Russia

16.68

13.61

69.71

43.45%

United States

18.99

14.88

66.13

51.21%

The dependency ratio describes how much pressure an economy faces in supporting its non-productive population

Dependency ratio limitations

  • It assumes that people under 15 years and over 65 years (65+) are outside of the labour force

    • UK has a retirement age of 67 years (and set to increase) and minimum working age and hours

  • It assumes that everyone aged 15-64 are working

    • UK has a school leaving age of 18 years 

Examiner Tips and Tricks

Don't worry about remembering population data, as it will have changed by the time of your exam. What is important is to remember the equation and what it shows. 

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