The BDI, or Baltic Dry Index is one of the less manipulated numbers out there, unlike GDP, Unemployment data, and CPI (Inflation), its much harder to fake. Unlike what the name implies, the index has nothing to do with the 'Baltic' region, yet everything to do with shipping capacity/rate/demand worldwide. Basically, in very simple terms, the higher the number, the more likely we have global growth.

A good interactive chart can be viewed over at Bloomberg.