Models of Population Change (AQA A Level Geography)

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

The Demographic Transition Model and Explanations of Population Change

Population Structure

• Another factor of population change is population structure, sometimes known as the age-sex composition
• Can be shown in a population pyramid

Features of 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

Application of Population Pyramids to Different Stages of the Demographic Transition Model

• 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