In a stacked line chart, multiple series are stacked vertically, as shown in Figure 8‑13. The stacked line chart shows totals for each series as well as the proportion that each series contributes to the grand total. In the example, the top line shows the total sales amounts for each quarter. The empty area between each line represents the sales amount for a region.

The stacked line chart is not as effective as the stacked area chart for comparing the amount that each region series contributes to the total because the areas are not shaded. In a stacked area chart, the shaded areas provide a clear visual cue that each part is compared to the whole.

In addition, as the example shows, a user can easily misinterpret the data in a stacked line chart. There is no obvious indication that the top line shows the total sales amount for each quarter and that the middle line shows the difference in the sales amount between Europe and Asia. A user viewing this chart can misinterpret the top line to represent the sales data for the U.S., the middle line to represent the sales data for Europe, and the bottom line to represent the sales data for Asia.