Presentation on theme: "Section 1b Age/ sex Structure. Learning outcomes To discover how population changes through time in relation to births, deaths and migration How population."— Presentation transcript:
Section 1b Age/ sex Structure
Learning outcomes To discover how population changes through time in relation to births, deaths and migration How population pyramids present age/ sex structure How population pyramids enable comparisons to be made over time
Population changes in time Population is dynamic…. It changes constantly over time and space How? Births Deaths Migration
Births, deaths and migration The total population of an area is the balance between two forces of change: natural increase (births- deaths) and migration Crude Birth rate: the number of live births per 1000 people per year Crude death rate: the number of deaths per 1000 people per year
Migration Migration does not affect the world population It affects the way in which people are distributed around the world It may lead to an increase or decrease in population in an area.
The Demographic Transition model The DTM describes a sequence of changes over a period of time in the relationship between births, deaths and overall population change. It was based on western Europe and USA It suggests that countries follow through a particular cycle
Demographic Transition Model Stage 1Stage 2Stage 3Stage 4 TIME BIRTHS AND DEATHS PER 1000 PER YEAR Birth rate Death rate Total population
Stage 1 Both death and birth rates are high giving small population growth Examples: Ethiopia, Bangladesh, UK pre 1760
Stage 2 Birth rate remain high but death rates fall to about 20 per 1000 Examples: Peru, Sri Lanka, Kenya and UK
Stage 3 Birth rates fall rapidly to 0 per 1000 and death rates fall slightly to 15 per slowly increasing population Examples: China, Cuba and Australia, UK
Stage 4 Birth and death rates remain low, fluctuating slightly to give a steady population Examples: Canada, Japan, USA and UK post 1940
Stage 5? Birth rates fall below death rates to give a declining population Examples Germany and Sweden
Problems with the model Its “Eurocentric”- a lot of the LEDC’s will not pass through all 4 stages Stage 5 is now possible Countries such as Malaysia and Hong Kong developed at a much faster rate than the model suggests
Population Pyramids The population structure of a country is best illustrated by a population or age- sex pyramid It is useful as it can predict short and long term changes in the population The DTM shows only natural increase the pyramids show the effects of migration, age and sex of migrants and effects of wars and epidemics.
The models are structured to show 'snapshots' of population at four points during its development, which are shown as Stages in the DTM