Population Pyramids? How they work!

If you're, like so many of youth today, a GCSE Geography Student, then this is bound to come up somewhere in your course.
Population Pyramids: to put it simply; A chart where Y is age and X is female-male. The 'Pyramid' bit comes from it's design. Due to there being less old people than youth, the chart seems to thin the further up you go. Making a "Pyramid" shape.

The Population Pyramid is split into two graphs: MEDC (More Economically Developed Countries) & LEDC (Less Economically Developed Countries)

The one to our left is the MEDC Pyramid. The one to the right is, quite obviously, the LEDC one.

Now, there are some factors that are obvious just by looking at the graph. The first is, the LEDC one is much, much more steep, more like the Empire State Building. While the MEDC one is buffed out on all sections, except the over 80's, where it starts to thin upwards. (LEDC Pyramid is a graph of Mozambique population) (MEDC Pyramid is a graph of Britain's population)

Secondly, the LEDC graph has a large 0-9 section - with more than 2.3 million children. But this significantly drops in periods 10-14, then again in 15-19, to round about's 1.3 million. That means approximately one million children that are born in Mozambique don't live over teenager age. Why?

There are many reasons for low life expectancy in Mozambique. It's in an continent where many countries suffer from severe poverty (Africa) and is close to some of the most poverty stricken countries in the world, such as: Zimbabwe, Tanzania, Uganda, Kenya and Botswana. This means many children die of illness and disease.
The large decrease has other factors, including that many LEDC families have around 8 (average) children - the main reason is because the mother knows only 1-2 will survive the poverty. Crime and youth armies are also two factors that decrease the population. With many teenagers being took from their homes into African armies/tribes.

The MEDC graph also has a "baby-boom" period, in the 30-40's. How did this occur? After WWII, in 1945, many women were relieved to see their husbands back home. Very relieved. And so the happiness took over and many expressed the need to have a baby. This create a huge population boost in 1946 - with around 3 million more babies being born that year. Now, 70 years on, many of the children in the War boom have had children. These children are now 30-40 years old.

The main point on the Y graph is the age difference. On the MEDC graph, it goes up to 100+, whilst on the LEDC graph it sticks to 80+ - This is due to nearly nobody in the LEDC's getting past 80 years of age. With only around 300,000 people reaching that age in Mozambique. The MEDC graph will go to 100+ because of the "elderly population" Britain has, where there is more people aged 50-54 then 0-4. There is also approximately 1 million people over the age of 80 in Britain, while in Mozambique it's only a third of that figure.

That's what Population Pyramids are, I hope you liked this short, brief tutorial on them. They're simple once you understand the concept of the graph. Good luck Geographers!