I was traveling quite a lot recently, and last week, read the Wall Street Journal cover to cover for the first time in a while. I am happy to report that there are many more data graphics than I remember of past editions.
The following chart illustrating findings of an FCC report on broadband speeds has a number of issues (a related blog post containing this chart can be found here):
The biggest problem with the visual elements is the lack of linkage between the two components. The two charts should be connected: the one on the right presents ISP averages by the broadband technology while the one on the left presents individual ISP results. Evidently, the designer treats the two parts as separate.
If that was the intention, there are two decisions that create confusion for readers. First, the charts use two different but related scales. Just add 100% to the scale of the left chart and you get the scale of the right chart. There really is no need for two different scales.
Secondly, orange and blue are used in both charts but for different purposes. In the left chart, orange denotes all ISPs whose actual speeds were below their advertised speeds. In the right chart, orange denotes ISPs using DSL technology.
I also do not understand why some ISP names are bolded. The bolded companies include several cable providers (but not all), several DSL providers (but not all), one fiber provider and no satellite.
Lastly, I'd prefer they stick to one of "advertised" and "promised". I do like the axis labels, saying "faster than" and "slower".
One challenge of the data is that the FCC report (here) does not provide a mathematical linkage between the technology averages and the ISP data. We know that 91% for DSL is the average of the ISPs that use DSL as shown on the left of the chart, but we don't know the weights (relative popularity) of each ISP so we can't check the computation.
But if we think of the average by technology as a reference point to measure individual ISPs, we can still use the data, and more efficiently, such as in the following dot plot where the vertical lines indicate the appropriate technology average:
(The cable section should have come before the DSL section but you get the idea.)
The key message of the chart, in my mind, is that DSL providers as a class over-promise and under-deliver.
In a Trifecta Checkup, this is a Type V chart.