World Population Growth

Natural population increase: When birth rates are higher than death rates, like in stage 2 and 3 of the DTM.

Natural population decrease: When death rates are higher than birth rates, like in stage 5 of the DTM.

A country's population can also be changed by immigration and emigration, but when there is reference to natural change, it only refers to changes caused by birth rates and death rates.

Population explosion or population bomb: The rapid growth in population, this might refer to the rapid growth of the world's population in the lat 100 years, or the rapid population growth of just one country.•Reasons for high birth rates include:
Lack of education about family planning
•Poor availability of contraception and cost of contraception
•Polygamy amongst some ethnic groups
•Primary based economy
•High rate of sexual violence often leading to unwanted pregnancies
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Reasons for declining death rates include:
Better testing for and treatment of HIV/AIDS
•Improved water supply
•Improved housing (although large numbers still live in informal settlements)
•Better education about diet


South Africa also receives large numbers of migrants from countries like Zimbabwe, Mozambique and Swaziland. This is either because of lack of economic opportunities in these countries and/or political problems.
















What is population structure and population pyramids?
•Population structure is usually shown using a population pyramid. A population pyramid can be drawn up for any area, from a whole continent or country to an individual town, city or village.
•Population structure means the 'make up' or composition of a population. Looking at the population structure of a place shows how the population is divided up between males and females of different age groups.


Young Dependents: The number or the percentage of the population under the age of 16.

Old Dependents: The number or the percentage of the population over the age of 65.

Economically Active: People between the ages of 16 and 65. This is basically the working group.

Obviously some people stay at school past the age of 16, some people retire before 65 and some people work after 65. Also some people between 16 and 65 might unemployed. However, when we are look at entire populations we have to look at averages (the norm).

Dependency Ratio: The ratio between the amount of dependents (old and young) and the economically active.







Key things to know about population pyramids
•The shape of a population pyramid can tell us a lot about an area's population.
•It gives us information about birth and death rates as well as life expectancy.
•A population pyramid tells us how many dependants there are. There are two groups of dependants; young dependants (aged below 15) and elderly dependants (aged over 65).
•Dependants rely upon the economically active for economic support.


•Many LEDCs have a high number of young dependants, whilst many MEDCs have a growing number of elderly dependants.




How do pyramids change over time?
•A population pyramid that is very triangular (eg Mozambique in 2000) shows a population with a high number of young dependants and a low life expectancy.
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•A population pyramid that has fairly straight sides (more like a barrel) shows a population with a falling birth rate and a rising life expectancy.
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•Over time, as a country develops, the shape changes from triangular to barrel-like.
• Places with an ageing population and a very low birth rate would have a structure that looks like an upside-down pyramid




Migration: The movement from one location to another location.

There are many different types of migration. The most commonly referred to are:


Rural-urban migration: This is a type of internal migration. It is the movement of people from rural areas

(the countryside) to urban areas (towns and cities). In the settlements topic we look at the causes, problems

and solutions of and to rural-urban migration in Rio de Janeiro.
International Migration: Migration between countries e.g. El Salvador to US.

Temporary Migration: Migration for a limited period, this might only be for a few weeks or even several years.

Permanent Migration: Migration with the intention of staying forever.

Forced Migration: When people are forced to migrate, often because their life is in danger.

Voluntary Migration: When people freely choose to migrate e.g. for better weather or better universities.

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