Age–Sex Pyramids and Population Analysis
Age–sex pyramids visually represent the distribution of different age groups in a population, categorized by gender.
These pyramids help identify trends in population growth, aging, and economic sustainability.
Dependency Ratio
Definition
Dependency ratio
The dependency ratio is a measure of the proportion of dependents (people under 15 and over 64) to the working-age population (15–64 years). It is calculated as:
$$\text{Dependency Ratio} = \frac{\text{Population aged 0–14 and 65+}}{\text{Population aged 15–64}} \times 100$$
Impact of High and Low Dependency Ratios:
- High Dependency Ratio:
- Found in countries with very high birth rates (e.g., Niger, Uganda) or aging populations (e.g., Japan, Italy).
- It increases the economic burden on the working-age population.
- Low Dependency Ratio:
- Occurs in countries with a balanced working-age population.
- It leads to economic growth potential (e.g., India’s demographic dividend).
Population Momentum
Definition
Population momentum
Population momentum refers to continued population growth even if the fertility rate declines.
It occurs because a large proportion of the population is in reproductive age, ensuring that births continue for several decades.
Example
- China: Despite implementing the one-child policy (1979–2015), the population continued to grow due to a high number of young women entering reproductive age.
- India: Even though fertility rates have declined, a large base of young people ensures continued growth before eventual stabilization.
Identifying Dependency Ratio and Population Momentum in Age–Sex Pyramids
Age–sex pyramids visually represent a population’s structure and can be analyzed to identify dependency ratios and population momentum by looking at specific patterns.
1. Identifying the Dependency Ratio
High Dependency Ratio:
- A wide base (many young people under 15) indicates a high youth dependency ratio (e.g., Niger, Uganda).
- A wide top (many elderly over 64) indicates a high elderly dependency ratio (e.g., Japan, Italy).
- A classic pyramid shape with a broad base and tapering top suggests a high overall dependency ratio.
Low Dependency Ratio:
- A bulging middle section (large working-age population, 15–64 years) suggests a low dependency ratio, meaning fewer dependents per worker (e.g., India, China).
- This is often seen in countries experiencing a demographic dividend, where economic growth potential is high.
2. Identifying Population Momentum
Signs of High Population Momentum:
- A wide base (large number of young people under 15) means that even if fertility rates drop, the population will continue to grow because many of these young people will soon enter reproductive age.
Example
India, Nigeria, and many developing nations show this pattern.
Signs of Low or Negative Population Momentum:
- A narrow base with a wider middle or top means fewer children are being born, leading to slower or negative population growth.
Example
Japan, Germany, and South Korea, where fertility rates are below replacement level (2.1 children per woman), meaning the population will eventually shrink.
