We all know this to be true (at least on a superficial level, since we often seem to forget). But Tyler Vigen has put some fun examples on Internet of time series that are correlated but where a causal relationship between the two is extremely unlikely.
For example, the chart below shows that the number people who drowned by falling into a swimming-pool correlates pretty strongly across the years with the number of films in which the legendary Nicolas Cage appeared.
Check out his website here for more.
— Michael R. Strain is a resident scholar and economist at the American Enterprise Institute. You can write to him on Twitter at twitter.com/MichaelRStrain.