An obscure gauge of shipping costs rose to prominence in geeky macro circles during the financial crisis because its plunge provided a telling lead on the economic crash that unfolded in 2008 and 2009. Now, the Baltic Dry Index has again taken a nosedive, falling to its lowest level in more than two decades.

This time, analysts are explaining it away as a reflection of an increased number of carriers at sea.

Julian Jessop at Capital Economics, acknowledges this has indeed been a big factor behind the index’s decline. Still, he suggests the magnitude of the drop should give forecasters some pause.

We think it would be wrong to dismiss entirely the warning signals that the sinking of the Baltic index is sending about the underlying demand for commodities and the health of the world economy more generally. If the BDI fails to rebound soon, now that the peak of the holiday season has passed, it may well be telling us something important about the health of the global economy after all.