Stack Graphs let you visualize quantitative changes to several data sets over time and simultaneously see how each data point contributes to the total. For example, Stack Graphs are a useful way to look at revenue or gross profit figures over time across several product lines. The Percentage Area Graph variant on the Stack Graph is an excellent choice when you need to understand the relative contribution for each data set in the series regardless of the absolute total. You can see trends that you might miss in other visualizations.