Source: Cullinane, K. and M. Khanna “Economies of Scale in Large Containerships”, Journal of Transport Economics and Policy, Vol. 33, pp. 185-207.

Average Cost per TEU by Containership Capacity and By Route, 1997

The above figure illustrates how economies of scale in container shipping are achieved by using larger containerships. For long distances, the cutting point is around 4,000 TEU. Even if the marginal benefits of using larger containerships appear relatively small after 4,000 TEU, the larger number of carried containers creates multiplying effects. It is thus not surprising that maritime shipping companies have introduced larger and larger containerships, particularly over long distance routes. The key limitation is now the capacity of port terminals to handle larger ships since this requires substantial investments in transshipment and port-side facilities. Theoretically, a vessel of 12,000 TEU on a long distance route would generate about 11% cost saving per container slot compared to a 8,000 TEU vessel, and even 23% compared to a 4,000 TEU vessel.