Please, please, please stop using pie charts to try to visualize ratios! See here[0] from 2007 for better alternatives. I'm sure there are newer visualizations as well.
[0]: https://www.perceptualedge.com/articles/visual_business_inte...
[0]: https://www.perceptualedge.com/articles/visual_business_inte...
http://www.storytellingwithdata.com/blog/2011/07/death-to-pi...
http://www.businessinsider.com/pie-charts-are-the-worst-2013...
https://qz.com/1259746/when-should-you-use-a-pie-chart-accor...