This is the most important global bellwether that no-one sees - And it just collapsed

Someone somewhere once joked that if you had to produce an economic report but wanted no one to read it, you’d probably call it something like “The Beige Book”. Appropriately, this regular update of US economic activity – the latest of which is published at 7pm tonight (GMT) – is usually about as tedious as it sounds.

Similarly, if I had to produce a barometer of global economic health but wanted no one to look at it, I’d probably call it “The Baltic Dry Index”.

But bear with us here, because something exciting has happened to the Baltic Dry Index of late (yes, really...)

It collapsed nearly 40 per cent during the opening nine days of trading this year, you see – a monumental New Year’s hangover, and the worst start to a year for over three decades. Perhaps it’s not so dry after all.

Anyway – why should you care about an index that measures the cost of shipping raw materials around the world? Good question. The answer is simply because, as alluded to above, these prices are used as an indicator of global economic health to come. A higher reading equals more demand for metals and stuff which are then made into products that we buy, the money from which is reinvested, and so on and so forth.

Conversely, a lower reading is portentous, suggesting weaker demand and slower economic growth.

The BDI, as it’s known, has never recovered post-Lehman. It plummeted from a reading above 11,500 down all the way to around 1,000 in the wake of the bank’s collapse five and a bit years ago.

In the final months of last year it began to edge up again, but – despite a reported rise of 0.3 per cent today – it has dived since.

The drop seems to bode ill for the global recovery this year, suggesting that perhaps the optimism towards the end of 2013 was over-stated.

There are some disclaimers, however. The index can be affected by micro events, such as a tiff in Colombia over the loading of coal onto ships. So don't get too carried away and flog all your stocks.

Nonetheless, while you shouldn’t become too bearish quite yet, this recent downward movement is a little concerning – and the index is certainly one to watch.