The Demographic Transition Model (DTM)

Mr Elliott

SSOT

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.

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

The model itself

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.

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

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).

Population pyramids