population pyramids
one way of looking at population change is with a type of graph called a population pyramid.
it is called a pyramid because that used to be the most common shape.
we can see this shape with Japan's population in 1950 in chart A. the population was largely young then, and it was the countryside. In these rural areas, children often worked together with their parents and helped to produce the food, goods, and household products
that the family needed. there were many diseases without cures and these often killed children, so families were large to increase the chance that some children would live to become adults.
In chart B, the pyramid for the year 2000 shows a big difference from the previous chart. there are two reasons for this change. First, children increasingly went to school instead of working. Rather than add to the family estate,children became an expense. Second, new medicines cured children,s like smallpox, measles, and polio, so large families were no longer needed.