Ever since Al Gore made himself a centimillionaire pushing a chart showing the rise in atmospheric CO2 correlated with a (bogus) hockey stick graph purporting to show global temperature rise, we have had to be on guard against matching graph trendlines. The Website Spurious Correlations has published a set of hilarious graphs matching clearly unrelated phenomena that appear to track each other with sometimes startling exactness. My two favorites are below, but the entire page is well worth a look:

Number of people who died by becoming tangled in their bedsheets
correlates with
Total revenue generated by skiing facilities (US)

Number people who drowned by falling into a swimming-pool
correlates with
Number of films Nicolas Cage appeared in