Population structure refers to the composition of a population in terms of age, gender and other demographic characteristics. One of the most useful ways to visualise population structure is through population pyramids, which show the distribution of different age groups in a population, separated by gender.
Key Definitions:
Population pyramids are bar charts that show the percentage or actual population of males and females in different age groups. Males are traditionally shown on the left and females on the right. The shape of a population pyramid can tell us a lot about a country's population and its stage of development.
The horizontal axis shows the population numbers or percentages, while the vertical axis represents age groups. The youngest age groups are at the bottom and the oldest at the top. The width of each bar represents the size of that age group relative to the total population.
Population pyramids reveal information about birth rates, death rates, life expectancy and dependency ratios. They can also help predict future population trends and highlight issues like ageing populations or youth bulges.
There are three main shapes of population pyramids, each associated with different stages of demographic development:
Wide base that narrows sharply towards the top. Indicates high birth rates, high death rates and a rapidly growing population. Typical of developing countries like Nigeria or Afghanistan.
Narrower base with a bulge in the middle. Shows declining birth rates, low death rates and an ageing population. Common in newly industrialised countries like Brazil or Mexico.
Similar proportions across most age groups until older ages. Indicates low birth rates, low death rates and slow population growth. Seen in developed countries like Japan or Germany.
Population pyramids change shape as a country moves through the stages of the Demographic Transition Model (DTM). This model describes how populations change as countries develop economically.
Countries in the early stages have expansive (pyramid-shaped) population structures with a wide base due to high birth rates. Death rates begin to fall in Stage 2, leading to rapid population growth. Examples include many sub-Saharan African countries.
As countries develop, birth rates fall, creating constrictive (bell-shaped) pyramids. In the final stages, both birth and death rates are low, leading to stationary (rectangular) pyramids with ageing populations. Examples include most European countries and Japan.
When analysing population structure, geographers look at several key indicators:
Total Dependency Ratio = ((Population aged 0-14 + Population aged 65+) ÷ Population aged 15-64) × 100
Youth Dependency Ratio = (Population aged 0-14 ÷ Population aged 15-64) × 100
Elderly Dependency Ratio = (Population aged 65+ ÷ Population aged 15-64) × 100
A country's population structure has significant implications for its development and planning:
Countries with young populations (expansive pyramids) face challenges like providing education, healthcare and eventually jobs for large numbers of young people. However, they may benefit from a future "demographic dividend" when these young people enter the workforce.
Countries with ageing populations (stationary pyramids) face different challenges, including increased healthcare costs, pension provision and a shrinking workforce. They may need to adjust retirement ages, encourage immigration, or implement policies to increase birth rates.
Japan has one of the most rapidly ageing populations in the world. Its population pyramid has a narrow base and bulges towards the top, creating an "inverted pyramid" shape. Over 28% of Japan's population is aged 65 or older.
Challenges: Labour shortages, high healthcare costs, declining tax base and rural depopulation.
Responses: Encouraging women to join the workforce, developing robotics and AI to address labour shortages, raising the retirement age and offering incentives for families to have more children.
Nigeria has a classic expansive pyramid with a very wide base that narrows sharply. Over 40% of Nigeria's population is under 15 years old.
Challenges: Providing education and healthcare for a large young population, creating enough jobs and managing rapid urbanisation.
Opportunities: Potential for a "demographic dividend" if the young population can be educated and employed productively, leading to economic growth.
Population structures are not static they change over time due to various factors:
Understanding population structure helps governments and planners prepare for future needs:
Population pyramids help predict future needs for schools, hospitals, housing and transport. A bulge in certain age groups indicates increased demand for specific services in the future.
Understanding the future size of the workforce helps with economic planning. Countries can prepare for changes in the dependency ratio and implement policies to address potential issues.
When analysing a population pyramid, ask yourself these questions:
In your IGCSE Geography exam, you might be asked to describe and explain population pyramids, compare pyramids from different countries, or discuss the implications of different population structures. Remember to use specific terminology and refer to real-world examples to support your answers.
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