Chart of the week: Population Pyramids, Vases and Wedges
Population pyramids show population data by gender and age group. They are effective in showing changes over time. This chart of Japan demographics through 2050 appeared in The Economist:
This shows three pyramids: Male on left, right hand side females from 1950, 2005, and 2050. (2050 is projection based on current trends). From 1950 to 2005, the pyramid turned into a vase shape until 2050 when it is projected to be an inverted pyramid or wedge. What this visualizes is the aging of Japanese society — in a pyramid, the society has a large base of younger people. For the wedge, the base is inverted as the society ages, lives longer, and has lower fertility rates.
A variant of the chart was produced by the National Institute of Population and Social Security Research that shows three different population models for 2050, based on different fertility assumptions:
A time-lapse view of the chart is here.
An interesting view of the patterns of population growth is in this diagram:
This series of patterns shows population growth, stasis and decline.
One way I can think of improving the charts is to add a horizontal axis to show the male/female percentages by age band and also indicate average number of children by parental age by a color/shading within te band.