A not-so-satisfying rose
Light entertainment: what is truth?

Rethinking the index data, with modesty and clarity in mind

I discussed the rose chart used in the Environmental Performance Index (EPI) report last week. This type of data is always challenging to visualize.

One should start with an objective. If the goal is a data dump, that is to say, all you want is to deliver the raw data in its full glory to the user, then you should just print a set of data tables. This has traditionally been the delivery mechanism of choice.

If, on the other hand, your interest is communicating insights, then you need to ask some interesting questions. One such question is how do different regions and/or countries compare with each other, not just in the overall index but also in the major sub-indices?

Learning to ask such a question requires first understanding the structure of the data. As described in the previous post, the EPI is a weighted average of a bunch of sub-indices. Each sub-index measures "distance to a target," which is then converted into a scale from 0 to 100. This formula guarantees that at the aggregate level, the EPI is not going to be 0 or 100: a country would have to score 100 on all sub-indices to attain EPI perfection!

Here is a design sketch to address the question posed above:


For a print version, I chose several reference countries listed at the bottom that span the range of common values. In the final product, hovering over a stripe should disclose a country and its EPI. Then the reader can construct comparisons of the type: "Thailand has a value of 53, which places it between Brazil and China."

The chart reveals a number of insights. Each region stakes out its territory within the EPI scale. There are no European countries with EPI lower than 45 while there are no South Asian countries with EPI higher than 50 or so. Within each region, the distribution is very wide, and particularly so in the East Asia and Pacific region. Europe is clearly the leading region, followed by North America.

The same format can be replicated for every sub-index.

This type of graph addresses a subset of the set of all possible questions and it does so in a clear way. Modesty in your goals often helps.



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What do the varying shades of the stripes signify? I can't quite tell if it's redundant encoding of the rank, or something else.

I like this concept a lot.
With some interactivity and drill down capability, this would be a really effective tool.

Cole Nussbaumer Knaflic

I have the same question - are color and horizontal position depicting the same thing? If so, you may be able to use color to encode regions and put all on the same line (though may not work if many are overlapping). Nice approach!


The color is a redundant coding of the scale, as you correctly inferred. I am experimenting with redundancy, inspired by something Noah Veltman said when he visited my class. Apparently readers like redundancy. It can be a good way of emphasizing a message and in this case, makes the chart more pleasing compared to a set of black stripes. But of course, it could lead to potential confusion as people might wonder if there is a hidden dimension!

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