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Introduction to population pyramids

Introduction to population pyramids






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    Introduction to population pyramids Introduction to population pyramids Presentation Transcript

    • Population Pyramids
    • Population Pyramids
    • What are Population Pyramids?
      • The population composition or structure of a country
      • population pyramid or age-sex pyramid
    • Males and Females
      • Figures for males are recorded on the left of the diagram.
      • Figures for females are recorded on the right of the diagram.
    • Males and Females
    • Sex Ratio
      • The division between the sexes can also be analysed by calculating the
      • male : female ratio
      • or sex ratio
      • This expresses the number of men in the population as a proportion of the number of women.
    • Horizontal Axis
      • The horizontal axis may either represent
      • actual numbers
      • OR
      • the percentage of
      • the total population in each age category.
    • Actual Numbers
    • Percentage
    • Vertical Axis
      • The population is normally divided into five year groups e.g. 0-4, 5-9, 10-14 on the vertical axis.
      • However, sometimes you will see one and ten year intervals too.
      • The final years are collapsed into one category (e.g. 90+)
      • Different age groups are known as cohorts
    • Five Year Cohorts
    • Population Pyramids Developing Countries
      • Wide base which indicates a youthful population (as a result of high birth rates);
      • Narrow top (there are fewer people in the older age groups because life expectancy is lower);
    • Sudan – a typical developing country pyramid
    • Implications for governments in developing countries
      • Limited resources will be stretched to meet the needs of a large number of dependent children for schooling, nutrition and health care;
      • As this group reaches working age, a large number of jobs will need to be created to enable them to support themselves and their families.
      • As this group reaches child-bearing age, it is likely that fertility rates will be high , leading to continued high rates of natural population increase.
    • Population Pyramids Developed Countries
      • Narrower base (due to lower birth rate)
      • Wider top (reflecting a longer life expectancy)
      • In some developed countries there is a bulge in 40-45 age cohort as a result of the “baby boomers” of the 1960s
    • Japan – a typical developed country pyramid
    • An ageing population
      • The issues faced by many developed countries is of an ageing population where a smaller proportion of the population are of working age and are faced with the task of generating enough wealth to provide high levels of support for the elderly population.
    • Dependency Ratio
      • The ratio of non-economically active to economically active people in the population is called the dependency ratio.
    • Zero Population Growth
      • The population pyramid can also show zero-growth.
      • This means that birth rates and death rates cancel each other out.
      • In this case, the age-sex pyramid is more like a column than a pyramid, and people are distributed evenly throughout the cohorts
    • Developed and Developing Countries
    • Past, Present and Future Trends
      • As well as illustrating the effect of past changes, population pyramids can also indicate both short and long term future changes in population.
      • We can use population pyramids to show the results of migration
    • Canada change over time
    • Characteristic of Population Pyramids - Summary
      • A wide base suggests a high birth rate, a high proportion of young people and thus a rapidly growing population
      • A narrow base tells us that the birth rate has fallen
      • Straight or near vertical sides tell us that the death rate is low
      • Sides that narrow inwards from the bottom show a high death rate
      • Large numbers of males around 20-34 year groups suggest high rates of immigration.
      • A small number of young people indicates high rates of outmigration