There a lots of interesting points to see in there :
- one can easily spot the future public retirement plans problem in Europe (with more and more elderly people ). See here for example : http://populationpyramid.net/?country=Belgium&year=2050
- I am still wondering what is happening in countries like Qatar in 2010 (http://populationpyramid.net/?country=Qatar&year=2010) How come there are so many more men than women ?
- Near 1950 in Europe, you can spot the "dent" made by WW2 in the population, plus the baby boom. Example : http://populationpyramid.net/?country=France&year=1950
- It is already interesting to compare the shape of the pyramid for countries like Afghanistan in 2010 (http://populationpyramid.net/?country=Afghanistan&year=2...) VS the US in 2010 (http://populationpyramid.net/?country=United_States_of_Ameri...). One can easily see the difference in development, to say the least.
And so on...
And marked dent you see in the 30 to 34 bracket in western europe in 1950 is not from WW2, but from WW1 (reduced births due to absent men).
It typically consists of two back-to-back bar graphs, with the population plotted on the X-axis and age on the Y-axis, one showing the number of males and one showing females in a particular population in five-year age groups (also called cohorts). Males are conventionally shown on the left and females on the right, and they may be measured by raw number or as a percentage of the total population.