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   04/4/2008 4:30 PM


     Bumps Charts

Introduction to Bumps Charts

Tufte, in Envisioning Information (pg 111), shows an example bumps chart and explains the origins of this powerful chart type ..

" ..the engaging bumps chart tallies results of English collegiate rowing contests. Bumps races come about because the narrowness of rivers preclude more than two crews from rowing side-by-side; in fact on bends there may be room for only one boat. At the beginning of a race, crews are spaced apart at intervals, the starting gun is fired, and they row like mad trying to catch the boat immediately in front. When a boat overtakes another, the crew in front pulls over and the one formerly behind goes on by, now in pursuit of the next boat ahead."

Click chart to go to site

The chart on the right is an example bumps chart for races held in May, 2005.

The direction of the daily lines indicate the boats results, raising lines indicate an advance,  declining lines indicate a reduction and horizontal lines indicate no change.

Even if you are not interested in crew races, the power of these charts shows up by looking at the results for boat 23 (champs). This boat had an advance each day, readily visible by the consistently rising line.



Non Racing Uses for Bumps Charts

Are there practical uses for bumps charts? Kaiser Fung at JunkCharts, an advocate for bumps charts, has shown several interesting practical examples of bumps charts, including the reconstruction below. Kaiser converted the difficult to interpret double doughnut chart on the left to the understandable bumps chart on the right.

Excel Bumps Chart Examples

Based on JunkCharts examples, I have developed several Excel bumps chart to demonstrate the power of these charts to highlight comparisons between sets of data over time or between conditions.

Example 1: Boston Public Schools: 1995 & 2005 (Source - Boston Globe, 6/15/06)

Clustered Column Chart Replaced with Excel Bumps Chart

Example 2: Boston Public Schools: Principal, Teacher and Student Race and Ethnic Makeup 1995 & 2005 (Source - Boston Globe, 6/15/06)

6 Pie Charts Replaced with 3 Excel Bumps Charts

Example 3:Auto Advertising Media Mix and Consumer Decision Impact - 2003 (Source: Truck and Barter)

Two Clustered Column Charts Replaced with Excel Bumps Chart