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# Introduction to population pyramids

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### Introduction to population pyramids

1. 1. Population Pyramids
2. 2. Population Pyramids
3. 3. What are Population Pyramids? <ul><li>The population composition or structure of a country </li></ul><ul><li>population pyramid or age-sex pyramid </li></ul>
4. 4. Males and Females <ul><li>Figures for males are recorded on the left of the diagram. </li></ul><ul><li>Figures for females are recorded on the right of the diagram. </li></ul>
5. 5. Males and Females
6. 6. Sex Ratio <ul><li>The division between the sexes can also be analysed by calculating the </li></ul><ul><li>male : female ratio </li></ul><ul><li>or sex ratio </li></ul><ul><li>This expresses the number of men in the population as a proportion of the number of women. </li></ul>
7. 7. Horizontal Axis <ul><li>The horizontal axis may either represent </li></ul><ul><li>actual numbers </li></ul><ul><li>OR </li></ul><ul><li>the percentage of </li></ul><ul><li>the total population in each age category. </li></ul>
8. 8. Actual Numbers
9. 9. Percentage
10. 10. Vertical Axis <ul><li>The population is normally divided into five year groups e.g. 0-4, 5-9, 10-14 on the vertical axis. </li></ul><ul><li>However, sometimes you will see one and ten year intervals too. </li></ul><ul><li>The final years are collapsed into one category (e.g. 90+) </li></ul><ul><li>Different age groups are known as cohorts </li></ul>
11. 11. Five Year Cohorts
12. 13. Population Pyramids Developing Countries <ul><li>Wide base which indicates a youthful population (as a result of high birth rates); </li></ul><ul><li>Narrow top (there are fewer people in the older age groups because life expectancy is lower); </li></ul>
13. 14. Sudan – a typical developing country pyramid
14. 15. Implications for governments in developing countries <ul><li>Limited resources will be stretched to meet the needs of a large number of dependent children for schooling, nutrition and health care; </li></ul><ul><li>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. </li></ul><ul><li>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. </li></ul>
15. 16. Population Pyramids Developed Countries <ul><li>Narrower base (due to lower birth rate) </li></ul><ul><li>WHY LOWER BIRTH RATES? </li></ul><ul><li>Wider top (reflecting a longer life expectancy) </li></ul><ul><li>WHY A LONGER LIFE EXPECTANCY? </li></ul><ul><li>In some developed countries there is a bulge in 40-45 age cohort as a result of the “baby boomers” of the 1960s </li></ul>
16. 18. Japan – a typical developed country pyramid
17. 19. An ageing population <ul><li>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. </li></ul>
18. 20. Dependency Ratio <ul><li>The ratio of non-economically active to economically active people in the population is called the dependency ratio. </li></ul>
19. 21. Zero Population Growth <ul><li>The population pyramid can also show zero-growth. </li></ul><ul><li>This means that birth rates and death rates cancel each other out. </li></ul><ul><li>In this case, the age-sex pyramid is more like a column than a pyramid, and people are distributed evenly throughout the cohorts </li></ul>
20. 23. Developed and Developing Countries
21. 24. Past, Present and Future Trends <ul><li>As well as illustrating the effect of past changes, population pyramids can also indicate both short and long term future changes in population. </li></ul><ul><li>We can use population pyramids to show the results of migration </li></ul>
22. 25. Canada change over time
23. 26. Characteristic of Population Pyramids - Summary <ul><li>A wide base suggests a high birth rate, a high proportion of young people and thus a rapidly growing population </li></ul><ul><li>A narrow base tells us that the birth rate has fallen </li></ul><ul><li>Straight or near vertical sides tell us that the death rate is low </li></ul><ul><li>Sides that narrow inwards from the bottom show a high death rate </li></ul><ul><li>Large numbers of males around 20-34 year groups suggest high rates of immigration. </li></ul><ul><li>A small number of young people indicates high rates of outmigration </li></ul>