Why it is time to retire Dr Copper

The red metal no longer tells investors much about the global economy

DOCTORS ARE famously reluctant to hang up their stethoscopes. But a time comes in the career of every medic when their skills fade, and a gentle push is the best thing for them—and their patients. The same applies for the metaphorical physicians of the financial world, whose ability to diagnose the market’s health changes over time. Now the end may be nigh for the most illustrious of all such physicians: Dr Copper.

Copper, a metal crucial to the construction of all manner of fittings, pipes and wires, has earned its nickname on Wall Street owing to its role as a bellwether for the health of global industry. A surge in copper prices is taken as an early sign of an economic upswing; a big drop is a portent of recession, or at the very least a manufacturing downturn.

So what is going on at the moment? Manufacturing looks peaky. Global industrial output is up by just 0.5% year on year, well below the average of 2.6% over the past two decades,…