Models of Population Change (AQA A Level Geography)

Demographic Transition Model

The Demographic Transition Model

•  The demographic transition model describes how, as countries develop, changes in birth and death rates subsequently affect population

  • The original model was devised in 1929

  • It showed how Western Europe and North America had gone through four stages of change since the start of the industrial revolution

  • A fifth stage has been added to a more recent version of the model

• Strengths of the model include:

  • It can be easily applied to different settings 

  • It can help demographers plan for predicted future changes

• Limitations of the model include:

  • It fails to take into account migration, natural disasters, pandemics, wars and government policies that impact birth rates, e.g. China’s one-child policy

  • It is based on countries in Western Europe that industrialised between 1800-1950

    • So it is harder to apply to newly emerging economies today that are industrialising in shorter time-frames due to globalisation

Population Structure

Population Structure

• Another factor of population change is population structure, sometimes known as the age-sex composition

  • Can be shown in a 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

Demographic Dividend & the Dependency Ratio

• The Demographic Dividend describes how when a country’s dependency ratio falls quickly it goes through a period of fast economic growth

• Population structures and pyramids can be divided into three age-group categories, depending on 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 depend on the economically active population can be measured 

  • This is expressed as the dependency ratio. 

• The dependency ratio tends to be:

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

    • Due to youthful population structure with many young dependents

    • E.g. 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

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

    • Due to a large elderly dependent sector of the population

    • E.g. in Japan the figure was 57 in 2021

  • Lower in newly emerging economies in stage 3 of the demographic transition model

    • 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

    • E.g. in Mexico the figure was 48 in 2021

• Countries going from stage 2 to 3 with falling dependency ratios have a chance of an economic boost due to the demographic dividend

  • This also requires political stability and investment in education and jobs

  • Examples include the Tiger economies of south-east Asia, as well as the BRIC countries