Thanks for including my redesign in your analysis. It's interesting to have your opinion on this chart and on scaling in general. I agree that it's a good opportunity to use a double-axis and I look forward to reading what you have to say about the second chart. I'm surprised so few people picked up on it.

Years of double-axis charts have trained me always to assume that when there's two lines on the chart, each one refers to a different axis. The Junkcharts version is really clever, but since both of the series and axes refer to the same underlying scale, it took me a second to figure out how to read it. Maybe it would help to place both the absolute-count and relative-proportion scales side by side on the right of the chart? Making the zero line stand out would have helped me orient myself too. As always, really love the blog!

Similarly, it's totally okay to have a Centigrade and a Fahrenheit scale. As Kaiser says, they scarcely count as "dual axis" at all.

I love the elegant simplicity of this; the graph's great, and a descriptive title means that the visualisation can be kept really clean. I do agree with spindoctors' comment; two axes implies two scales, so it would help to make it clearer one way or another that the numbers are different representations of the same scale.

I would also be inclined to visually differentiate the rate of change line and the magnitude line more than just having them as different colours.

Thanks very much for the insightful roundup.

Coming into this discussion a bit late .....

Visually, the charts by Keller and Voila, give a "truer" view. They visually emphasize that women'd CEO number only 4 % of the total. The charts also show that the proportion has remained disproportionately low through the period depicted.

While your chart is ingenious, it emphasizes the growth. It does not visually communicate that these CEOs form only 4%.

I had recently grappled with a similar issue in my last blog post - http://www.visualquest.in/2014/01/uniform-scale.html
Here we are plotting sales and profit numbers. Profit number will invariably be a smaller number. When the two are plotted side by side, we can only achieve one objective - give a sense of the right proportion [ but the slope indicating growth in the variable will be incorrect] or give a correct sense of growth [ where the proportion will be incorrect. ]

In the context of the financial report, the actual value and the proportion are paramount. However since profit is a lower number the growth rate [even if it is the same rate] will invariably appear lower. But presenting the actual values gives a "truer" value.

Just wanted to add that I wouldn't call this example an exception to the rule.

The rule really applies to plotting multiple series, with different measures, using different y axes to reflect those measures, on the same plot.

Here you're plotting one line, one measure, with two axes labeled in different manners to express the same information differently.

It may be obvious or understood, but I think it's an important distinction. It's an exception to the rule because it deals with circumstances that the "rule" doesn't address.

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

(Name is required. Email address will not be displayed with the comment.)

## NEW BOOTCAMP

See our curriculum, instructors. Apply.
Marketing analytics and data visualization expert. Author and Speaker. Currently at Columbia. See my full bio.

## Book Blog

Graphics design by Amanda Lee