Whats is a Pie Chart?
Its a 2 dimensional circular graphs which is used to compare or understand the size and the proportion of a category / dimension to its entire data set, generally use to measure “part-to-whole relationship”.
Fig1 : the above example shows us the work order status and % of orders that are currently in those stages.
While pie charts are certainly over used, but there are some specific and niche situations in which they are appropriate.
Pie charts should only be used to see comparisons between categories. In the above graph you would see that almost three quarters of the orders are “Completed” and about a quarter of the orders are “Pending”. You can visually see that no orders are “Declined”. But this should be the only reason to use pie charts.
Even Though from the looks of it you, you can clearly see that more than 50% of the orders are in “Confirmed” status. But it is hard to say how many orders exactly represent the pie. As the slivers keeps getting smaller and smaller, it is very difficult to understand the proportion of that category.
In order to avoid this you would create a legend. This would be great but you would now need to keep looking at the legend most of the time to tell you the proportion of the smaller slivers.
Another issue, that you would face is more the categories you have , the more colours are required and then even the legend starts to lose its value, as you cannot differentiate between dark blue and sky blue.
Fig2 : In the above chart it is very hard to to even see the slices of “quote” and “in progress” category.
4. Pie charts are also disadvantages when you have almost similar sized pies.
Fig3 : In the above chart it is very hard to say if the “Invoiced”, “New” and “Pending” categories are similar in proportions.