Proportional Area Charts usually use squares or circles. However, any shape can be used, so long as you use the shape’s area to represent the data.
A common technical error with area charts is to use one length to determine the shape’s size, when in fact you need to calculate the space inside the shape to determine its size. Otherwise, you will cause exponential increases and decreases.
Great for comparing values and showing proportions (in sizes, quantities etc) to give a quick, overall view of the relative sizes of the data, without the use of scales. The downside to this chart is that it’s difficult to estimate values using Proportional Area Charts. This means they’re almost exclusively used for communication purposes instead of analytical ones.