Pie Graphs of the U.S. Age Distribution

A pie graph shows how a whole divides into parts. The circle is the entire population and each slice is one age group, sized by its share. Reading across the three years, the slice for people over 65 grows from about a tenth of the country to a fifth, and that is the point the chart makes without requiring anyone to read the table.

Pie graphs are good at exactly this and poor at almost everything else. They cannot show a trend over time within one circle, and with more than a handful of slices they become unreadable. The slider pulls the slices apart, which makes the smaller ones easier to compare but loses the sense of a single whole.