A
pie chart (or a
circle chart) is a circular
statistical graphic, which is divided into slices to illustrate numerical proportion. In a pie chart, the
arc length of each slice (and consequently its
central angle and
area), is
proportional to the quantity it represents. While it is named for its resemblance to a
pie which has been sliced, there are variations on the way it can be presented. The earliest known pie chart is generally credited to
William Playfair's Statistical Breviary of 1801.