WHAT IS A POPULATION PYRAMID?

• A population/age sex pyramid is a graphical illustration of the distribution of a human population in a particular country or region at a specific time period (usually one year) .

• It is assessed in terms of age, which is generally measured on a five year interval (0-4, 5-9, 10-14 etc) and sex (male or female).

• It consists of two back-to-back bar graphs, on the left shows male while on the right shows female according to age group as a percentage of the total population, on the X-axis is population while is age on the Y-axis.

• It also tells how many people of each age group live in the area. For e.g. it can show economic dependents (under 15 ,full time education, and over 65, those who have the option of retirement.) and the working population (15-59).

• Moreover, it can be used to observe the natural increase, birth, and death rate .

• At the top there is title showing country or region.• On the left shows males and the right shows

females according to year group as a percentage of the total population.

• On the X-axis population is showed in millions. While on the Y-axis age is grouped in 5 year intervals (0-4,5-9, 10-14)

Types of population pyramids

There are generally three types: Expansive Constrictive Stationary

EXPANSIVE These show larger percentages of the

population in the younger age groups, usually with each group smaller in proportion than its predecessor. These have a Broad base.

This type is usually found in populations with:• very large fertility rates • lowlife expectanciesFor e.g. this may be seen in Latin American and

many Third World countries.

Constrictive

These display a lower percentage of young people whilst a higher percentage of the elderly is recorded. These are Top-heavy.

This may be so due to :• A declining birth and death rate.• A high life expectancyFor e.g. United States and Canada

STATIONARY

These display somewhat equal percentages for almost all age groups.

Of course, smaller figures are still to be expected at the oldest age groups due to old age deaths.

For e.g. European countries such as Sweden and Germany.

The Demographic Transition Model

• It describes a sequence of changes in birth, death rate and population change as a country changes from pre-industrialized to an industrialized economic system.

• It was developed by an American demographer Warren Thompson (1887-1973).

• He observed that over 200 years many countries in Western Europe went through similar stages and predicted that in time all countries will pass through the following four stages.

STAGE 1 : High Fluctuating/ Pre Transition

Birth rate are: Lack of Family Planning High Infant Mortality Rate Children are needed as

labour Some religious beliefs

encourage a large family

Death rate are: High levels of diseases Famine Lack of Sanitation and Clean

water Lack of Healthcare

This is the most primitive stage. There is a high birth and death rate and a slow population growth. Reasons for a high:

STAGE 2 : Early Expanding/ Early Transition

Birth rate remains high but the death rate is falling while the population begins to rise steadily.

Reasons for a fall in the Death Rate are:Improved HealthcareImproved HygieneImproved SanitationImproved Food Production

STAGE 3: Late Expanding/ Middle Transition

Birth rate begins to fall while death rate continues to fall and population rises even more.

This is because there is an: Increased mechanisation (reduces need for

workers)Increased desire for material things less desire

for a large familyEmancipation of women to follow careers rather

than be child bearers.

STAGE 4: Low Fluctuating/ Late Transition

Birth Rate are:

Children are expensive Lower infant mortality rate

Death Rate are: Better Healthcare Better standards of living

There is a low birth rate.There is a low death rate.The population is steady.

THANK YOU

By Leanna Rampa

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