And, of course, some correlations happen to be completely random. If enough data sets are compared, sooner or later there will be two that match almost perfectly completely by accident. There is even a Spurious Correlations website, which can search through publicly available data and find matches for you. I did a quick check against the number of people in the United States who obtained a PhD in mathematics. Between 1999 and 2009, the number of math doctorates awarded had an 87 percent correlation with the “Number of people who tripped over their own two feet and died.” (Provided without
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