If we were going to see a stock market crash in the United States in the fall of 2015 (to use a hypothetical example), we would expect to see commodity prices begin to crash a few months ahead of time. This is precisely what happened just before the great financial crisis of 2008, and we are watching the exact same thing happen again right now. On Wednesday, commodities got absolutely pummeled, and at this point the Bloomberg Commodity Index is down a whopping 26 percent over the past twelve months. When global economic activity slows down, demand for raw materials sinks and prices drop.  So important global commodities such as copper, iron ore, aluminum, zinc, nickel, lead, tin and lumber are all considered to be key “leading indicators” that can tell us a lot about where things are heading next. And what they are telling us right now is that we are rapidly approaching a global economic meltdown.

If the global economy was actually healthy and expanding, the demand for commodities would be increasing and that would tend to drive prices up.  But instead, prices continue to go down.

The Bloomberg Commodity Index just hit a brand new 13-year low. That means that global commodity prices are already lower than they were during the worst moments of the last financial crisis…

The commodities rout that's pushed prices to a 13-year lowpulled some of the biggest mining and energy companies below levels seen during the financial crisis.

The FTSE 350 Mining Index plunged as much as 4.9 percent to the lowest since 2009 on Wednesday, with BHP Billiton Ltd. and Anglo American Plc leading declines. Gold and copper are near the lowest in at least five years, while crude oil retreated to $50 a barrel.

“This commodity bear market is like a train wreck in slow motion,” said Andy Pfaff, the chief investment officer for commodities at MitonOptimal in Cape Town. “It has a lot of momentum and doesn't come to a sudden stop.”