1. Chapter 2 Key Issue 3
Why Is Population Increasing at Different Rates in Different Countries?

2. Demographic Transition Model
The demographic transition model explains changes in the natural increase rate as they relate to economic and industrial development.
It is a process with four stages and every country is in one of them.

3. Stage 1
Stage one of the demographic transition is one of high birth rates and death rates and consequently very low growth.
Most of human history was spent in stage one but no countries remain in that stage.

4. Stage 2
Stage two is one of high growth because death rates decline and birth rates remain high.
The demographic transition assumes that countries enter stage two because they go through the Industrial Revolution. Technologies associated with industry helped countries to produce more food and improve sanitation and health.

5. Stage 2
Western European countries and North America entered stage two about 1800.
Countries in Latin America, Africa, and Asia have experienced stage two much more recently, and without experiencing an industrial revolution.
Developing countries have moved into stage two because of a medical revolution, the diffusion of medical technologies to LDCs.

6. Stage 3
Countries will move from stage two to stage three when their crude birth rates drop sharply as a result of changes in social and economic patterns that will encourage people to have fewer children.

7. Stage 4
Countries will reach stage four of the demographic transition because their birth rates will continue to decline until the natural increase rate drops to zero. This is true of countries in Europe together with Canada, Australia, and Japan.
The demographic transition assumes that this occurs because of more changes in social customs such as women entering the labor force in large numbers.
It could be argued that some countries, primarily western and northern European, that are now experiencing population decline, have entered stage 5.

8. The Age –Sex Distribution
The age-sex distribution of a country’s population can be shown on a population pyramid. It will show the distribution of a country’s population between males and females of various ages.
A population pyramid will normally show the percentage of the total population in five year age groups with the youngest group at the base of the pyramid and the oldest group at the top.
Males are usually shown on the left and females on the right.
Each age –sex group is called a population cohort.

9. Age-Sex Distribution
A pyramid with a wide base shows a rapidly growing country with a large proportion of young people, and is typical of a less developed country. A pyramid that is more rectangular depicts a country with relatively even number of young, middle-aged, and older people, and is typical of a more developed country.
The dependency ratio is the number of people in a population under the age of 15 and over the age of 64, compared to the number of working people who must support them.