Trade imbalances. They are probably the most important source in the accumulation of empty containers in the global economy. A region that imports more than it exports will face the systematic accumulation of empty containers, while a region that exports more than it imports will face a shortage of containers. If this situation endures, a repositioning of large amounts of containers will be required between the two trade partners, involving higher transportation costs and tying up existing distribution capacities.
Repositioning costs. They include a combination of inland transport and international transport costs. If they are low enough, a trade imbalance could endure without much of an impact as containers get repositioned without much of a burden on the shipping industry. Repositioning costs can also get lower if imbalances are acute as carriers (and possibly terminal operators) will offer discounts for flows in the reverse direction of dominant flows. However, if costs are high, particularly for repositioning container inland, shortages of container may appear on export markets.
Revenue generation. Shipowners allocate their containers to maximize their revenue, not necessarily the economic opportunities of their customers. In view of trade imbalances and of the higher container rates they impose on the inbound trip for transpacific pendulum routes, shipowners often opt to reposition their containers back to Asian export markets instead of waiting for the availability of an export load. For instance, while a container could take 3 to 4 weeks in the hinterland to be loaded and brought back to the port and earning an income of about $800, the same time can be allocated to reposition the container across the Pacific to generate an return income of $3,000.
Manufacturing and leasing costs. If the costs of manufacturing new containers, or leasing existing units, are cheaper than repositioning them, which can be possible over long distances, then an accumulation can happen. Inversely, higher manufacturing or leasing costs may favor the repositioning of empty containers. Such a condition tends to be temporary as leasing costs and imbalances are correlated.
Usage preferences. A large number of shipping lines uses containers as a way of branding the company name and to offer readily available capacity to their customers. This observation combined with the reluctance of shipping lines and leasing companies to share market information on container positions and quantities for competitive reasons, makes it very difficult to establish container pools or to widely introduce the ‘grey box’ concept. Still, as demonstrated by the North American rail system (TTX rail equipment pool), it is possible for transport companies to distinctly separate container assets from modal assets so that the efficiency (such as the turnover rate) can be improved.
Slow steaming. Excess capacity and rising bunker fuel prices have incited maritime shipping companies to reduce the operational speed of their containerships from 21 knots to 19 knots, a practice known as slow steaming. The resulting longer transoceanic journeys tie more container inventory in transit, incite transloading in proximity of port terminals and reduce the availability of containers inland.