Here I excerpted the left half of an advertisement found in Institutional Investor. It is one of those ubiquitous ads touting one mutual fund or another. (Click on the ad to see a larger version of it.)
It illustrates the principle of subtracting by adding. Jam a chart with more data, particularly repetitive data, and confuse the hell out of the reader.
My eyes aren't sure where to focus. Are the bars important? With the blue ovals perched atop the bars, most of them appear to be the same height. Are the percentages in the blue ovals significant? What are they measuring? Annual returns? How is it that the bar heights are not correlated to the percentages?
If you're still paying attention, you might ask if the quartile ranking is the key message? What about the actual ranking shown at the bottom of the charts?
The unlucky few who scan all the fine print at the bottom will not get any of these questions answered either.
This is a kalediscopic chart. There is only one data series (ranking of each fund in its fund group) but this data is shown four times in four different guises:
- as an actual ranking listed at the bottom
- as percentiles written in the blue ovals
- as percentiles coded in the bar heights
- as quartiles requiring referencing the vertical axis
Indeed, by adding multiple representations, the original data graphic loses clarity.