Tuesday, May 22, 2007

Pre Release Question 6

For the next batch of questions, you need to look at Resources 2 & 3: a Population Pyramid, and a graph showing Natural Increase and Migration between 1991 and 2002.

Question 6

Q6) What does a Population pyramid show ?
Do you think it is a good way of showing data or not ? Explain

OK, so a population pyramid is essentially 2 bar graphs plotted back to back.
There is a MALE side and a FEMALE side, with population plotted by number (in this case, although sometimes it will be plotted as a percentage of the total) and age groups, which are more properly called COHORTS.

Sometimes these are in 5 year groups, sometimes in 10 year groups.

Check out this BBC BITESIZE guide to using Population Pyramids.
There's an INTERACTIVE one at the National Statistics site.

THIS SITE allows you to create pyramids for any country.

So why are they called pyramids ? They look nothing like one...
Well, if you look at the pyramid for other countries, particularly ELDCs (poorer countries economically speaking...) they tend to have a higher birth rate and a higher death rate, and a lower life expectancy, and this changes the shape.
The fact that the UK's population does not look like a pyramid tells you a lot about our changing population

What do we think of them as a way of representing data ?
We thought they were better than a line graph (such as the one below from the National

I came across an interesting suggestion on a discussion forum looking at some alternative ways of showing the data. You can read it HERE if you're really interested in this idea.

This was to 'fold' the pyramid, so that the male and female pattern could be more easily compared, like the example below for the Portuguese city of Lisbon.

This allows you to see the difference in the upper age groups really well.
What other benefits are there of using coloured bars to represent the population of a particular age group ? What problems are created once you put the data into groups ?

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