Change over time can be expressed using a time series chart, which is a chart that represents data points in chronological order. Charts that express change over time include: line charts, bar charts, and area charts.

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Multiple types of charts can be suitable for depicting data. The guidelines below provide insight into how to choose one chart over another.
- Showing Change Over Time
- Bar and Pie Charts
- Area Charts

Selecting Charts

Showing change over time

Both bar charts and pie charts can be used to show proportion, which expresses a partial value in comparison to a total value.

Bar charts express quantities through a bar’s length, using a common baseline
Pie charts express portions of a whole, using arcs or angles within a circle
Bar charts, line charts, and stacked area charts are more effective at showing change over time than pie charts. Because all three of these charts share the same baseline of possible values, it’s easier to compare value differences based on bar length.

Bar and pie charts


Area charts come in several varieties, including stacked area charts and overlapped area charts:

Stacked area charts show multiple time series (over the same time period) stacked on top of one another
Overlapped area charts show multiple time series (over the same time period) overlapping one another
Overlapping area charts are not recommended with more than two time series, as doing so can obscure the data. Instead, use a stacked area chart to compare multiple values over a time interval (with time represented on the horizontal axis).

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