REUTERS/Svitzer/Handout
Shipping is a good indicator of how the global economy's doing
You might guess it's related to shipping - and you'd be right.
The BDI is a very useful gauge of global trade, and tells you how much it costs to move goods around the world in massive ships. These goods can be pretty much anything: iron ore, grain, coal ... stuff the world needs to build things and function.
As such, analysts keen to predict how the health and future of the global economy like to pay close attention to it.
It is frequently used as a so-called canary in the coal mine for the state of the world economy and how well international trade is doing. If the price is low, it suggests trade is slowing.
And that's the problem. As this chart shows, right now it's doing really badly:
In fact this is the worst it's ever been. To put it in perspective, it was at 11,000 points in May 2008, just before the financial crash. Now, it's below 300.
This matters because BDI drops have historically predicted economic crashes. It did in 2008 and it did again last November when commodity and oil prices jumped off a cliff.
As usual, most people are blaming this on China. Two years ago, the country shipped in over half the world's iron-ore and 25% of its coal. But China grew by only 7.4% last year when previously it was running at well over 10%.
Exports from China have also plunged, dropping 25.4% in February from the same time last year.
Some say things may not be quite as bad as the chart suggests, though. As The Economist notes, the index takes into account the supply ships - and ships that transport thousands of tonnes of raw materials take years to build. In other words, the falling index is as much a result of shipping manufacturers' overestimation of demand than a lousy global economy.
Either way, the BDI shows the world is way too reliant on China's insatiable demand and that painful reality check isn't going away anytime soon.