gross tonnage确实还是容积吨的意思，但他答说是Compensated Gross Tonnage (CGT) ，可见他满脑袋糨糊！！
Compensated Gross Tonnage (CGT) is an indicator of the amount of work that is necessary to build a given ship and is calculated by multiplying the tonnage of a ship by a coefficient, which is determined according to type and size of a particular ship.
The standard CGT system was developed in 1977 by the OECD so that inter-country shipbuilding output could be reasonably compared, as different types of ships require a greater or lesser degree of work relative to their gross tonnage. For example, passenger ferry of a given size would require substantially more work to build than a bulk carrier of the same size due to the differing design requirements, internal structure, and required level of detail, but simply comparing the gross tonnage or deadweight of each ship would incorrectly show that they took the same amount of work. When expanded on a national scale, this difference could greatly mislead people as to the actual maritime production capacity of a given country.
