US fertility rate

In the space of a few decades, Last Christmas has climbed the charts as American fertility has climbed back down them. Whether this reflects any particular cultural truth or is simply the product of streaming math is left to the interpretation of anyone with a credit card and a therapist. Mariah Carey, for the record, has better numbers.

Last Christmas's chart position has risen steadily as streaming made December more seasonally concentrated, while the US fertility rate has been in long-term decline with a particularly sharp 2020 drop as covid uncertainty pushed would-be parents to wait. Two unrelated trends that happened to look dramatic in the same pandemic year for entirely separate reasons. The common variable is time, not the song.

So the correlation is one metric about what people sing and another about what they stop having. Both describe the season. Only one of them is anybody's fault.