There’s a website that features a wide variety of spurious correlations that’s worth checking out:

My favorite is the margarine consumption correlation with divorce. Here the actual correlation is with financial hardship: loss of income is the independent variable and both margarine consumption & divorce are the dependent variables. When a household’s income takes a big hit, people economize. As margarine is cheaper than butter, consumption of the former increases. And as we all know, a lot of marriages fail to survive a financial hit, and so incidence of divorce also rises.

At other times, there’s no real linking factor at all and it’s just the random chance you’d expect if you trawl enough data sets. Personally I’d expect suicides to be strongly correlated with Nicholas Cage movie releases, but perhaps it’s easier simply not to watch them in the first place…

Anyone who enjoys my articles here on Medium may be interested in my books Why Democracy Failed and The Praying Ape, both available from Amazon.