In strategy consulting, we are trained to always use Stacked Bar charts for breaking up percentages. Why? Because then you can compare when you decide to add / remove time series. They can be compared over days, weeks, months, you can compare across two different subgroups.

Instead, it seems everyone in Silicon Valley likes to put pie charts in a presentation because they're round and design friendly. But I already basically know how I spent yesterday. What I want is to know how yesterday compared with previous days, how this week is tracking compared to previous weeks.

In summary, pie charts are worse than stacked bar charts and should be replaced across the app.