Introduction to population pyramids

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Transcript of Introduction to population pyramids

  • 1.Population Pyramids

2. Population Pyramids 3. What are Population Pyramids?

  • The population composition or structure of a country
  • population pyramidorage-sex pyramid

4. Males and Females

  • Figures formalesare recorded on theleftof the diagram.
  • Figures forfemalesare recorded on therightof the diagram.

5. Males and Females 6. 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.

7. Horizontal Axis

  • The horizontal axis may either represent
  • actual numbers
  • OR
  • the percentage of
  • thetotal populationineach age category.

8. Actual Numbers 9. Percentage 10. 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 ascohorts

11. Five Year Cohorts 12. 13. Population PyramidsDeveloping Countries

  • Wide basewhich 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);

14. Sudan a typical developing country pyramid 15. Implications for governments in developing countries

  • Limited resourceswill be stretched to meet the needs of a large number ofdependent children for schooling, nutrition and health care;
  • As this group reaches working age,a large number of jobs will needto be created to enable them to support themselves and their families.
  • As this group reaches child-bearing age, it is likelythat fertility rates will be high , leading to continuedhigh rates of natural population increase.

16. Population PyramidsDeveloped Countries

  • Narrower base (due to lower birth rate)
  • WHY LOWER BIRTH RATES?
  • Wider top (reflecting a longer life expectancy)
  • WHY 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

17. 18. Japan a typical developed country pyramid 19. An ageing population

  • The issues faced by many developed countries is of anageing populationwhere 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.

20. Dependency Ratio

  • Theratioofnon-economically activetoeconomically activepeople in the population is called the dependency ratio.

21. Zero Population Growth

  • The population pyramid can also show zero-growth.
  • This means thatbirth rates and death rates cancel each other out.
  • In this case, the age-sex pyramid is more like acolumnthan a pyramid, and people are distributed evenly throughout the cohorts

22. 23. Developed and Developing Countries 24. Past, Present and Future Trends

  • As well as illustrating the effect of past changes, population pyramids can also indicate bothshort and long term future changesin population.
  • We can use population pyramids to show the results ofmigration

25. Canada change over time 26. Characteristic of Population Pyramids - Summary

  • Awide basesuggests a high birth rate, a high proportion of young people and thus a rapidly growing population
  • Anarrow basetells 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 bottomshow 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