Last Christmas peak chart position

The annual revival of a 1984 Wham! single and the estimated population of a nearly-extinct whale species are not, on the face of it, linked. And yet, here they are, in statistical step. George Michael, posthumously, would be proud and confused.

Last Christmas's chart performance has climbed each year as streaming makes the holidays more concentrated, while the right whale population has been slowly declining due to ship strikes and entanglements — with 2020 data partly a survey artifact because covid halted aerial and ship-based population counts. Two unrelated trends that happened to bend sharply at the same time for very different reasons. One kept climbing. The other was just harder to count.

So the correlation is a reminder that some numbers go up because we stream them, and others go down because we stopped measuring. Both arrive looking like trends. Neither is what it seems.