By then, it is estimated that there will be some 8000 ships in operation with a total slot capacity of nine to ten million standard containers. There will be approximately the same number of containers ashore being packed or unpacked, awaiting stuffing or unstuffing or being transferred. The majority of these containers are standard 20' box containers. While there are special containers for many applications, growth rates for these are not significant.
From the standpoint of container traffic, it would be ideal for there to be a balance between incoming and outgoing containers in a particular region, not only in terms of numbers, but also in terms of container type and weight. Unfortunately, such a balance is not achievable. There will thus always be empty containers to be transported in one direction or another. From the shipping company's standpoint, general purpose containers usable in any circumstances would be a major advantage. Forwarders, on the other hand, would prefer special containers if they could be carried at identical cost, as packing and securing is much easier in a special container than in a standard container.
For example, steel sheet in coils can very quickly be loaded onto coil containers and straightforwardly secured. They are rather more difficult to pack and secure on flatracks, while they are particularly difficult to pack and secure in box containers. Shipowners accepting containers loaded with coils for transport to Colombia would, if the rolls of sheet steel were shipped in coil containers, also have to take a large number of empty standard ventilated containers to Colombia in order to transport coffee from Colombia to Europe. Moreover, the coil containers, which are of no further use in Colombia, would have to be transported empty to somewhere where they could be used again. As a result, steel sheet in coils will be transported to Colombia in "coffee containers" which are less suitable for carrying such cargoes.
Another example: in order to save on the higher freight costs associated with using tank containers, flexitanks are placed inside normal standard box containers, the walls of which are frequently damaged by surging of the liquid in the flexitanks.
A further example: containers exported from Europe to East Asia are, on average, heavier than those imported from East Asia. If it is to be possible to export the bulkier cargoes from East Asia, empty containers will have to be transported to East Asia. If many 40' containers are required to carry "light" cargoes from East Asia to Europe, it is sensible also to use these containers in Europe to carry "heavy" cargoes to East Asia. Users of these containers get plenty of transport space, the volume of which is not actually required, plus a "securing problem" because such containers cannot be tightly packed.
The majority of the world's container stocks are owned by shipping companies. Quite a few are, however, leased in both large and small numbers to shipowners or other interested parties by leasing companies. Some forwarders ship goods in their own containers, but these are generally special containers for bulk cargoes, tank containers for chemicals or beverages or coil containers for the steel industry etc.