After further analysis it turns out that the correlation...

After further analysis it turns out that the correlation increases with MC purely because producers tend to have large MC's and explorers/developers smaller MC's.

Another plot of the correlation vs MC for a larger set of companies is shown below. This is done for 21 asx listed producers and 23 asx listed non-producers, GOLD producers obviuosly for 12 month data.

I found all the goldies I could find, the ones I missed had no trades on too many days.

Note the large no. of producers above the line of best fit (as indicated with a -P)and the Large number of non-producers below the line of best fit.

The 4 indicated producers are the only producers substantially below the line of best fit. The 2 indicated explorers are the only explorers substantially above the line of best fit

The plot below shows that generally producers are more correlated with gold than non-producers

There is no indication for producers separately or non producers separately that the correlation increases with MC.
(i.e.CTO-MC-$72, IAU-MC-$422, 2 lowest producer correlations)

Goldies included (not all strictly goldies)

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