Population Pyramids. With a world population of more than 7 billion dispersed across more than 190...
17
Population Pyramids
-
Upload
myles-armstrong -
Category
Documents
-
view
215 -
download
0
Transcript of Population Pyramids. With a world population of more than 7 billion dispersed across more than 190...
Population Pyramids
Population Pyramids
• With a world population of more than 7 billion dispersed across more than 190 countries of various shapes and sizes around the globe, it is necessary to determine a method to compare countries equally.
• What are Population Pyramids?– A graphical representation of population data– Display population data by age and gender– a paired horizontal bar graph– Uses percentages of males and females for each age
group– Can be used for predicting future population trends
COHORT
• A group of people of a certain age
• Used to determine trends and see similarities and differences
• 5 year groups are most common
How to Read a Population Pyramid
• Bar graphs are a handy way to illustrate numbers. For example, if we were to graph the number of males and females in Canada for various age groups according to the 1961 Census.
Population Pyramid
• If we were to display these graphs horizontally, make a mirror image of the one for women, and then join them together, we would have a population pyramid
• You can see that the pyramid narrows toward the top. This is because the death rate is higher among older people than among younger people.
• There are also a few bulges and narrower parts in the middle part of the pyramid. For example, there are not as many people in their 20s as in their 30s in Canada in 1961. The people in their 20s in 1961 were born during the Depression, a time of economic hardship in Canada when people were having fewer children.
• In 1961, the pyramid had a wide base. In fact, when we add the percentages for the three lowest age groups, we find that 35% of the population was under 15. These are the “baby boomers,” a large group of people born between 1947 and 1966 when the economy was growing and prospering.
Population Pyramid
http://www12.statcan.ca/english/census01/products/analytic/companion/age/cda01pymd.cfm
• What seems to happen to the pyramid by the late 1940s?
• Can you account for the shape of the pyramid in 2001?
• Does it look like a pyramid anymore?
• What shape do you think the population pyramid might resemble in 25 years? In 50 years?
Population Pyramids
• There are 3 main shapes for a population pyramid:
– Rapid growth: wider at the bottom of the pyramid; shows a young population
– Slow growth: relatively equal (looks almost the same at the top and bottom); population now growing much
– Stable/Declining: wider at the top than the bottom (population is shrinking)
Three Shapes of Population Pyramids
RAPIDLY EXPANDING
• Very high birth rate• Population growing very fast (3-4% per year)
• Low income countries
EXPANDING
• High birth rate
• Population growing (1-2% per year)
• Middle to low income countries
STATIONARY
• Births replace deaths• Population not changing much at all• High income countries
DECLINING
• More deaths than births• Population shrinking• Potential social problems
Population pyramids can also be influenced by:
• Migration: Likelihood of extra young males as these are likely to migrate.– Example of Migration Case Study – from Developing Countries
to Developed Countries– Documentary: ‘Which Way Home’– http://www.cbc.ca/documentaries/passionateeyeshowcase/
2010/whichwayhome/index.html
• Famines: Clear drops in population especially among the very young as these are most likely to suffer.
• War: Clear drop off in male populations of fighting age.
