Today Adobe showed how hard it is to make a proper datavisualisation. I received their newsletter about their infographic and datavisualisation templates.
To start off with their first example. Take a look at the left piechart.
The 30% pie-chart pieces (blue and yellow) are not the same size. Probably the maker mistakenly put the 40% in the red part instead of the blue one. It’s not very obvious and this is one of the reasons why a bar-chart would have been a better choice in this example; piecharts are hard to read when the pie-parts are similar in size.
Their other example looks nice, but how do we read a chart like this?
If the percentages wouldn’t have been there, could you have guessed how much bigger the largest iceberg was compared to the small one? And do we need to interpret just the top of the iceberg or the entire iceberg? Our minds are not very good at comparing area’s. Furthermore, the sizes of the icebergs and the bubbles with the percentages seem off. The icebergs are the hardest to compare, the first one has a more or less circle shape, while the last one is taller compared to the width.
I also tried to compare the bubbles and I even measured them to try to find the logic behind the sizes. To calculate the size of a bubble designers often use the diameter, but that won’t give you the right proportions. On wikipedia they explain it as follows:
“The human visual system naturally experiences a disk’s size in terms of its area. And the area of a disk—unlike its diameter or circumference—is not proportional to its radius, but to the square of the radius. So if one chooses to scale the disks’ radii to the third data values directly, then the apparent size differences among the disks will be non-linear (quadratic) and misleading.”
However, neither the diameter nor the area can explain the sizes above. So maybe the designer just used intuition? And that’s the only way to use a chart like this: for an emotional, rough comparison. But make sure the proportions are a bit more accurate than this one.