GEOGRAPHY (9696) STUDY NOTES: CORE HUMAN GEOGRAPHY (POPULATION)

The Demographic Transition Model (DTM): Understanding Population Change

Hello Geographers! This topic is all about understanding how human populations change over time as societies develop. The Demographic Transition Model (DTM) is one of the most important concepts in population geography—it’s essentially a roadmap showing how birth rates and death rates shift, and it’s guaranteed to come up in your exams!

Don't worry if the term "demographic transition" sounds complicated. It just means the historical shift from high birth and death rates to low birth and death rates in countries that industrialise and urbanise.

Why is the DTM Important?
  • It helps us predict future population growth (or decline).
  • It links population changes directly to social and economic development.
  • It helps governments plan for services like healthcare, education, and pensions.

1. Key Concepts and Measures

To understand the DTM, we first need to define the two main forces driving natural population change:

1.1 Birth Rate and Death Rate

The DTM is fundamentally based on the interplay between two rates, usually measured as Crude Rates (meaning they are calculated for the entire population, not just a specific group).

A. Birth Rate (BR)

The number of live births per 1,000 people in a population per year.

  • High BR Factors: Lack of contraception, need for labour (especially in farming), high Infant Mortality Rate (IMR) meaning families have "replacement" children, cultural/religious beliefs favouring large families.
B. Death Rate (DR)

The number of deaths per 1,000 people in a population per year.

  • High DR Factors: Disease, famine, poor sanitation, war, lack of medical care, lack of clean water.

1.2 Natural Increase (or Decrease)

When the BR is higher than the DR, the population is growing. This is called Natural Increase. If the DR is higher than the BR, the population is shrinking (Natural Decrease).

(Remember: The DTM only considers natural change, not migration!)

Quick Review: Key Terms

Natural Increase Rate (NIR) = (Birth Rate - Death Rate) / 10

(We divide by 10 if the rates are out of 1000 to get a percentage growth rate.)

2. The Five Stages of the Demographic Transition Model

The DTM is usually shown as a graph where the BR and DR lines cross over five distinct periods. Let’s break down what happens in each stage, focusing on the changes in BR, DR, and overall population size.

Stage 1: High Stationary

This stage represents pre-industrial, traditional societies.

  • BR: High (often 35-50 per 1000). Why? Children are assets (needed for farming), high IMR necessitates many births, lack of family planning.
  • DR: High and fluctuating (often 35-50 per 1000). Why? Recurring epidemics, famine, poor hygiene, little medical knowledge.
  • Natural Change: Zero or very low increase. Population growth is flat (or stationary).
  • Example: No country remains entirely in Stage 1 today, but some remote tribal groups might exhibit these characteristics. Historically, the world was in Stage 1 until the late 18th century.

Stage 2: Early Expanding

The start of development, driven by the Agricultural and Industrial Revolutions (historically).

  • BR: Remains High. Social traditions (large families) take time to change.
  • DR: Falls Rapidly. Why? Key improvements in sanitation (clean water), hygiene, and food supply/transportation reduce infectious diseases dramatically.
  • Natural Change: Very Rapid Increase. This is the population boom stage, where the gap between the high BR and falling DR is widest.
  • Example: Many of today's Least Developed Countries (LICs), such as Niger or Afghanistan.
Memory Aid: Why does DR fall before BR?

It’s easier and faster to prevent people from dying (e.g., distributing vaccines, providing clean water) than it is to convince people to have fewer children (which requires economic change, education, and cultural shifts).

Stage 3: Late Expanding

Societies become more urbanised and developed. The process of limiting family size begins.

  • BR: Falls Rapidly. Why? Children are now an economic cost (not an asset), urbanisation means less need for farm labour, increased access to contraception, rising status/education for women, IMR falls (so fewer replacement births needed).
  • DR: Falls Slowly. It can't fall as fast as Stage 2 because the easiest gains (sanitation) have already been made.
  • Natural Change: High but slowing down. Population growth continues, but the rate of increase begins to decline significantly.
  • Example: Many Middle Income Countries (MICs) or Newly Industrialised Countries (NICs) like Brazil or India.

Stage 4: Low Stationary

This stage represents highly developed, industrialised countries.

  • BR: Low and fluctuating. Family size is small, women focus on careers, high availability of contraception.
  • DR: Low and fluctuating. High standards of living, excellent healthcare, and good diets.
  • Natural Change: Zero or very low increase. The population is stable again (stationary), but at a much larger number than in Stage 1.
  • Example: Most High Income Countries (HICs) like the USA, UK, and France.

Stage 5: Declining (Natural Decrease)

This stage was added later as some HICs experienced fertility rates falling far below the replacement level.

  • BR: Very Low. (Below replacement level of 2.1 children per woman). Factors include economic uncertainty and late marriage/childbearing.
  • DR: Slightly increasing/low. Why? Due to advanced medical treatments, people live longer, leading to an ageing population. As the population gets older, the overall death rate rises slightly despite good healthcare.
  • Natural Change: Natural Decrease. The population begins to shrink naturally.
  • Example: Countries like Japan, Germany, and Italy.

3. Links to Population Structure (Age/Sex Diagrams)

As a country moves through the DTM, its population structure (shown by population pyramids) changes dramatically. Understanding these changes is crucial, especially regarding dependency ratios (Syllabus 4.2).

Stage 1 & 2: Youthful Structure

The pyramid has a very wide base and rapidly slopes inwards (like a traditional pyramid).

  • High percentage of dependents under 15 (youth dependency).
  • Needs: High investment in schools and maternity healthcare.
Stage 3: Transitional Structure

The base starts to narrow, but the working-age groups (15-64) are very large (the "bulge").

  • This is the Demographic Dividend—a large potential workforce compared to dependents.
  • If managed well, this population can boost economic growth.
Stage 4 & 5: Ageing Structure

The base is narrow or even inverted, and the top (older ages) is wider. It often looks like a rectangle or a barrel.

  • High percentage of dependents over 65 (elderly dependency).
  • Needs: High investment in pensions, geriatric care, and hospitals.

Did you know?
The dependency ratio is a measure of the number of people who are too young or too old to work, compared to the working-age population. Stage 5 countries, despite being wealthy, face severe problems due to high elderly dependency ratios.

4. Critical Appreciation of the Demographic Transition Model (DTM)

A "critical appreciation" means looking at the model's strengths but also its weaknesses and limitations. In A-Level Geography, you must be able to evaluate the model, not just describe it.

4.1 Limitations of the DTM

While helpful, the DTM is a generalisation based primarily on the experience of Western industrialised nations (like the UK). It doesn't fit every country perfectly.

1. Eurocentric Assumption (The Original Path)

The model assumes that all countries follow the same path from Stage 1 through Stage 4, at the same pace. This is often not true.

  • Example: In 19th-century Europe, the transition took over 100 years. Today, some LICs (like South Korea or Thailand) have moved from Stage 2 to Stage 4 in just 50 years due to rapid technological transfer and international aid (especially medical aid).
2. Exclusion of Migration

The model only considers Natural Increase. It ignores the huge impact of international and internal migration, which can drastically alter population size and structure, especially in small, wealthy countries (like Qatar, which has a huge influx of young male workers).

3. Policy and External Factors

The model doesn't account for government policies that artificially speed up or slow down the transition.

  • Example: China’s former One-Child Policy enforced a rapid reduction in the BR, moving the country quickly through Stage 3. This was not a "natural" transition.
4. Variability of Stage 5

The model was originally designed with only four stages. Stage 5 is a modern addition, and not all developed countries are in it (some fluctuate in Stage 4). The severity of the population decline and the long-term sustainability of Stage 5 populations are still hotly debated.

5. The Role of Economic Development

The DTM implies that economic development (industrialisation) *causes* lower death rates and then lower birth rates. However, in some contexts, social changes (like women's education) can drive down birth rates before large-scale industrialisation occurs.

Key Takeaway: Critical Appreciation

When you evaluate the DTM, remember it is a model—a simplification of reality. It is a great starting point for comparison, but you must always use real-world case studies to show where and why countries deviate from the model’s predicted path.

Keep practising linking the causes (social/economic factors) to the effects (changes in BR/DR) for each stage!