8.1C Age-sex pyramids and demographic transition model Notes

Age-Sex Pyramids: Understanding Population Composition

It helps compare different societies and predict future demographic trends.

How to Read an Age-Sex Pyramid

Structure:

1. X-axis → Population size (absolute number or percentage).
2. Y-axis → Age groups (typically in 5-year intervals).
3. Left side → Males
4. Right side → Females

Types of Age-Sex Pyramids

Expanding Pyramid (Youthful Population)

1. Broad base → High birth rate.
2. Narrow top → Low life expectancy.
3. Common in developing countries (e.g., Nigeria, Afghanistan).
4. Challenges: Strain on education, healthcare, food supply.

Stationary Pyramid (Stable Population)

1. Narrower base but consistent width in reproductive ages.
2. Moderate birth & death rates.
3. Seen in developed nations with replacement-level fertility (e.g., USA, France).
4. Challenges: Need for sustainable job creation & resource management.

Contracting Pyramid (Aging Population)

1. Narrow base → Low birth rate.
2. Wider top → Aging population with high life expectancy.
3. Common in developed countries facing population decline (e.g., Japan, Germany).
4. Challenges: Labor shortages, rising elderly care costs, pension strain.

Applications of Age-Sex Pyramids

1. Government Planning → Allocating resources for healthcare, education, and jobs.
2. Economic Forecasting → Predicting workforce trends & dependency ratios.
3. Policy Decisions → Influencing policies on immigration, retirement age, and child benefits.

The Demographic Transition Model (DTM): A Framework for Understanding Population Change

1. The Demographic Transition Model (DTM) is a tool that helps us understand how populations change over time.
2. It describes the shifts in birth and death rates as societies progress through different stages of development.

By examining these stages, we can better understand the dynamics of human populations and their impact on the environment.

The Five Stages of the DTM

Stage 1: High Stationary

Characteristics:

1. High birth rates: Driven by the absence of birth control, high infant mortality, and cultural norms favoring large families.
2. High death rates: Caused by disease, famine, poor hygiene, and limited medical care.
3. Population Growth: Minimal, as high birth rates are offset by high death rates.

Stage 2: Early Expanding

Characteristics:

1. Declining death rates: Improvements in sanitation, food supply, and medical care reduce mortality.
2. High birth rates: Remain high due to cultural inertia and lack of access to contraception.
3. Population Growth: Rapid, as the gap between birth and death rates widens.

Stage 3: Late Expanding

Characteristics:

1. Declining birth rates: Access to contraception, improved healthcare, and women's empowerment reduce fertility.
2. Low death rates: Continue to stabilize at low levels.
3. Population Growth: Slows as birth rates approach death rates.

Stage 4: Low Stationary

Characteristics:

1. Low birth and death rates: Both rates stabilize at low levels.
2. High life expectancy: Due to advanced healthcare and living standards.
3. Population Growth: Minimal or stable.

Stage 5: Declining

Characteristics:

1. Very low birth rates: Often below replacement level (TFR < 2.1).
2. Stable or rising death rates: Due to an aging population.
3. Population Growth: Negative, leading to population decline.