In Worldyards, we have divided the world's merchant fleet by 21 segments such as bulker, tanker and container. Each segment is further broken down into sub-segments according to their capacity, their utility or unique features. Worldyards has tried to follow market naming convention to the extent possible, and we have consulted many experts in the shipping industry to arrive at the current set of definitions.
Normally tanker is treated as one segment, then it is divided further into "crude", product and others, then there are "sub sub" segments such as VLCCs under Crude.Worldyards has found that programming-wise it is very difficult to have 3 tiers in the logical tree, so we have to resort to breaking tanker into tanker I (crude), tanker II (product) etc. Having this two tier system make it possible for Worldyards to produce live sub-segment statistics.
Worldyard definition is not logically contineous - there are unfilled gaps in conceptual space, because in reality, no ships exist in that space. By way of example, we may call a ship > 100 <= 105 in loa (in MT) as one sub-segment, the next sub-segment could well be >=115 and < 200 - because there are simply no ships existing >105 and <115.
As a concrete example, there are no bulk carriers between 85,000 and 104,999mt <= 32,31 m with loa < 200m. So there is no provisions for ships thus defined.
We "invented" in order to find a home for all the vessels - both existing ships and orders. For instance, we added a subsegment called "post panamax tanker uncoated" - 64,999-85,000 with post-panamax beam (there are 29 ships such ships in the database). The simple reason for this is that it is too far fetch to call these ships "aframax" and we don't know where else to put them.
Suggestions from experts is also behind our decision to increase VLCC limit to 325,000 dwt.
We have assigned factor values according to the latest OECD CGT formula to all sub-segments except offshore, which form the basis of our shipbuilding capacity calculations.
It has really been an evolving process and we welcome input from all shipping practitioners to make the definitions as well as the CGT factors more logical, scientific sound and practical.
Just looking at the capacity figures in our definitions, at first glance, it may appear that some sub-segments are overlapping for bulkers, containerships and tankers. However, please note that we have also considered the "beam" and/or “loa” in our definition. For example, if you look at post-panamax vs panamax bulkers - the dwt limits are overlapping but aside from dwt, post-panamax bulker has beam greater than 32.31m whilst panamax has beam equal or less than 32.31m.