Slope Chart
Connects paired values across two points in time (or two categories) with lines, emphasizing direction and steepness of change.
Innovation Index 2015 vs 2023
Four countries' scores, before vs after
View data (8 rows)
| period | score | country |
|---|---|---|
| 2015 | 82 | USA |
| 2023 | 78 | USA |
| 2015 | 74 | Germany |
| 2023 | 81 | Germany |
| 2015 | 69 | Japan |
| 2023 | 85 | Japan |
| 2015 | 60 | Brazil |
| 2023 | 65 | Brazil |
Use a slope chart when…
- Comparing values or ranks between exactly two time points
- Highlighting which items improved, declined, or stayed the same
- Showing before/after comparisons for a handful of items
Avoid when…
- When you have more than two comparison points (use bump chart instead)
- When the number of items exceeds 15, causing heavy overlap
- When exact values matter more than relative change
Data it needs
| Property | Value |
|---|---|
| Min Rows | 6 |
| Min Columns | 3 |
| Column Types | stringnumbernumber |
| Notes | Requires an item label, a value for period 1, and a value for period 2. |
Visual anatomy
Guiding principles
Consider instead
Common mistakes
Overcrowding the chart with too many lines
Not sorting the left axis to reduce crossings
Omitting direct labels and relying only on a legend
History
Edward Tufte popularized slope graphs in his 1983 book 'The Visual Display of Quantitative Information,' showcasing them as a clean way to compare two time periods. The form has roots in parallel coordinates but distills the idea down to two axes.
Accessibility notes
Provide a data table showing each item's start value, end value, and change. Use thick lines with high contrast and consider adding arrowheads to indicate direction of change.
Related reading
Got data? Let's see what works.
Drop your CSV. You'll get a Slope Chart plus four alternatives - ranked by which one actually fits your data best.