For business presentations, we usually produce graphs that are easiest in Excel. But there is one graph that cannot be produced easily in Excel, but is far more powerful: the slopegraph (a term coined by Edward Tufte).
Slopegraphs are perfect when you want to contrast two sets of data, either showing how the data changes over time, or how two groups are different. It is basically a line chart with two time periods. But slopegraphs have many advantages over tables, bar charts and pie charts.
1. Better than Tables (change in rank)
You may want to show how two lists have changed, such as the how the top 15 business schools in the United States have changed over the past decade. You could show this data as a table, but then the mighty surge of Chicago (my alma mater) would be lost in the clutter.
A slopegraph is better.
- You can see at a glance which schools have risen and which have fallen in rank
- You can see which schools have risen or fallen most drastically
- You can see both lists ordered at the same time
- Chicago’s mighty surge is apparent to everyone
2. Better than a Bar chart (change in volume)
To show sales changes over time, you might use a column chart comparing quarter-over-quarter sales perhaps by year or by region. Side by side you can see the change in volume. You can even sort the bar chart with the worst performers at the front and the best performers at the end.
A slopegraph is better.
- You can see at a glance which regions are improving and which need attention
- Each list is ordered with the top perfomers at the top
- Height on the slide indicates their sales volume
- The direction and magnitude of change is instantly clear
3. Better than a Pie chart/stacked bar chart (change in proportion)
We often want to know how percentages are changing over time. Are we gaining or losing market share? Are we selling more of our high-price or low-price products? We often use side by side pie charts or side by side stacked bar charts.
A slopegraph is better:
- Pie slices and stacked bar layers cannot be compared side by side for exact (or even close) comparisons. For instance, in the charts above, is the “Professional” segment growing or shrinking? By how much?
- Slopegraphs require less color to differentiate the pie slices and stacked bar layers
There is no way to create slopegraphs automatically in Excel (Microsoft, are you listening?). Instead, you need to create them using the line graph in Excel, then manually add the labels and values.
In this blog article, I’ve shown you how to use slopegraphs when comparing values that change over time. In the next article on slopegraphs, I’ll show when they are superior to other graphs types when you compare two different groups at the same point in time. Subscribe to my blog to receive that article in your inbox.
About the author: Bruce Gabrielle is author of Speaking PowerPoint: the New Language of Business, showing a 12-step method for creating clearer and more persuasive PowerPoint slides for boardroom presentations. Subscribe to this blog or join my LinkedIn group to get new posts sent to your inbox.