Bloomberg compares people's lives in retirement in this interesting dataviz project (link, paywall). The "showcase" chart is a radar plot that looks like this:
The radar plot may count as the single chart type that has the most number of lives. I'm afraid this one does not go into the hall of fame, either.
The setup leading to this plot is excellent, though. The analytical framework is to divide the retirement period into two parts: healthy and not so healthy. The countries in the radar plot are in fact ordered by the duration of the "healthy retirement period", with France leading the pack. The reference levels used throughout the article is the OECD average. On average, the OECD resident retires at age 64, and dies at age 82, so they spend 18 years in retirement, and 13 of them while "healthy".
In the radar plot, the three key dates are plotted as yellow, green and purple dots. The yellow represents the retirement age, the green, the end of the healthy period, and the purple, the end of life.
Now, take 10, 20, 30 seconds, and try to come up with a message for the above chart.
Not easy at all.
Notice the control panel up top. The male and female data are plotted separately. I place the two segments next to each other:
It's again hard to find any insight - other than the most obvious, which is that female life expectancy is higher.
But note that the order for the countries is different for each chart, and so even the above statement takes a bit of time to verify.
There are many structural challenges to using radar charts. I'll cover one of these here - the amount of non data-ink baggage that comes with using this chart form.
In the Bloomberg example, the baggage includes radial gridlines for countries, concentric gridlines for the years dimension, the country labels around the circle, the age labels in the middle, the color legend, the set of arrows that map to the healthy retirement period, and the country ranks (and little arrow) that indicate the direction of reading. That's a lot of information to process.
In the next post, I'll try a different visual form.