Well, partly they are moving to the East Coast because it is cheaper to rail and truck them there than back to the West Coast and partly they never leave the West Coast ports near hinterland because shipping lines realised that the inland moves actually cost them money.

Exporters are reluctant to pay to have empty containers delivered to destinations that are not convenient for the import box. They are also reluctant to pay the full cost of transporting the boxes to the ports and then shipping at rates that more closely resemble market rates than in the past. This is the fundamental “shortage”. We also see that import destinations do not match export points of origin, a further cost issue that exacerbates the problem.

But there is more to it than that. The sudden jump in US exports cannot be a new found source of manufactured goods, those have been “globalised” to China. What we are experiencing is a surge in agricultural commodities (50% in value terms in the same period January to April) on the back of a collapsed dollar. These commodities are chasing containers. Why? Bulk rates for grain from the US Gulf to Japan in a supramax, 49,000 tonne ship increased from $55/tonne in January 2007 to $130/tonne in June. That makes containers attractive, but it is still hard to pay intermodal rates for a low value commodity.

Nevertheless, until bulk rates drop, or the dollar strengthens, we will continue to see grains and similar commodities increasingly move in containers; once they find them.