What is a pie chart?
A pie chart is a circular graph that shows the relative contribution that different categories contribute to an overall total. A wedge of the circle represents each category's contribution, such that the graph resembles a pie that has been cut into different sized slices. Every 1% contribution that a category contributes to the total corresponds to a slice with an angle of 3.6 degrees.
Source: Social Trends 30 - Visits to the most popular tourist attractions, 1981, 1991 and 1998, Table 13.14, Crown Copyright.