Merry Christmas, readers.
A Twitter follower pointed me to this visual:
I have yet to understand why the vertical axis of the top chart keeps changing scales over time. The white dot labelled "Peak 1982" (70 million) is barely above the other white dot for "2007" (38 million). This chart hides a clear trend: the population of sheep in New Zealand has plunged by 45% over 25 years.
To address the question of sheep versus human, one should plot the ratio of sheep-to-human directly. In this case, the designer probably faced a problem: because of the plunging population of sheep, the ratio has plunged steeply in 25 years. To make a point that "people are outnumbered more than 9 to 1", the designer didn't want to show a plunging trend. (Could this be the reason why the human population in 1982 was not printed?)
This is a case of too many details. Instead of manipulating the scale to distort the data, one can simply show the current ratio, or the average ratio in the last five years.
As the reader scans to the bottom set of charts, a cognitive wedge is encountered, as the curved scale of the New Zealand chart gave way to the normal uniform scale. These smaller charts are no less confusing, however.
The two lines on these two charts appear almost the same and yet, the Australian chart (on the left) shows a ratio of 4 to 1 while the Icelandic chart (on the right) shows a ratio of 1.5 times. Makes you wonder if each one of the small-multiples have a dual axis.
Again, I'm not convivned that the time series adds anything to the message.