Opportunity or Illusion?

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Take a look at this ratio chart of the XME divided by the GDX. Note the long-term range and its cyclic nature.

slopechart XME GDX

Below are the individual charts of XME followed by GDX.

slopechart XME
slopechart GDX

To the naive observer, the pairs trade would be to go long XME and go short GDX. Thoughts, Slopers?