2. The Demographic Transition Model (DTM) Mr Elliott SSOT

3. Population Changes The total population of an area depends upon changes in the natural increase and migration. The natural increase (or decrease) is the difference between the birth rate and the death rate. The birth rate is the number of live births in a year for every 1000 people in the total population. The death rate is the number of people in every 1000 who die in a year. If the birth rate is higher then the total population will increase. If the death rate is higher then the total population will decrease.

4. The Demographic Transition Model The DTM describes a sequence of changes in the relationship between birth rates and death rates. The model was produced using changes in the natural increase in several industrialised countries in western Europe and North America. It suggests that the population growth rates for all countries can be divided into four stages

5. The model itself

6. Population structures The rates of natural increase, births, deaths, infant mortality and life expectancy all affect the population structure of a country. The population structure of a country can be shown by a population or age- sex pyramid.

7. Population pyramids show The total population divided into five- year age groups the percentage of people in each of those age groups the percentage of males and females in each age group

8. Population pyramids are useful because they show: Trends in the birth rate, death rate, infant mortality rate and life expectancy - these trends can help a country to plan its future services, e.g. more homes for the elderly if there is an ageing population or fewer schools if there is a declining birth rate. The effects of people migrating into or out of a region or country. The proportion of the population who are economically active and the proportion who are dependent upon them (dependency ratio).

9. Population pyramids