Correction to: Nature Astronomy https://doi.org/10.1038/s41550-020-1203-3, published online 10 September 2020.

In the version of this Comment originally published, in Fig. 3b,c all the year values on the x axis had mistakenly been given as ‘1988’ and should instead have run from 1980 to 2020 in five-year increments. In addition, on the x axis of Fig. 4b the second instance of ‘1980’ should have been ‘1990’. All versions of the Comment have been amended.