Saturday, October 17, 2009

Population shapes




These interesting charts showing population age structure in various countries were published recently in the Times Saturday Magazine’s Crunch Time series.

They are similar to the one I lifted earlier to illustrate Population growth but include both sexes & show relative (%) frequencies rather than numbers in ‘000s.

It should also be noted that the vertical scale is not the same for each chart: those for Japan & UK have the scales stretched to go only from 0% to 9%, while that for Uganda is squashed down to go from 0% to 25% over the same distance. The horizontal scales (for age) are the same in each case. The picture would look different if all the scales were the same – a point which I used to enjoy demonstrating at the press of a key when we first got the ability to draw graphs on a teleprinter linked to a computer.

Why did Japan not have a Baby Boom in the 1960s? That must partly explain the recent low birth rates.

The UK looks boringly rectangular – a very settled state, apart from that 1960s boom.

India looks rather like just one half of a bell curve with σ quite large – a combination of high fertility balanced by higher mortality at younger ages?

The astonishing picture for Uganda – reflecting extraordinarily high birth rates & deaths from AIDS looks almost like a negative exponential – spookily, often used to model the failure time of manufactured items such as light bulbs.

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