Market power can come from buyers or sellers. In this case, China demand represents the entire deficit in copper relative to production. Nickels is more sensitive to EU and US slowdown given its higher usage at about 1/3 of global demand. Most metals like aluminum copper and zinc are 25%.
Correlation with equities have moved higher from about .3 to .5. Sensitivity to a one percent decline in equities is .8 for nickel and .45 for Aluminum.Speculative copper has fallen off a cliff and has moved from net long to net short.