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260 Third IMO GHG Study 2014
that ships are assumed to reduce their cargo load factor – i.e. become less productive – rather than being
scrapped/laid up or reducing their speed.
The projection of ship productivity is based on historical productivity of the ship types.
Historical ship productivity
A look at the historical productivity of the total world fleet reveals that it has seen dramatic variations over the
last five decades. During this period, the fleet’s productivity peaked in the early seventies with 35,000 tonnemiles
per dwt and reached a minimum in the mid-eighties with 22,000 tonne-miles per dwt (Stopford, 2009).
Productivity then increased until 2005/2006 but was far from reaching the peak from the early seventies.
Since then the productivity again shows a falling trend.
Figure 37: Historical fleet productivity (Stopford, 2009)
The historical productivity of the different ship types varies greatly.
Figure 38, Figure 39, and Figure 40 give the historical productivity of oil tankers, bulk carriers, container ships
and liquefied gas tankers.
Two data sources have been used to determine these productivities:
1 Tonne-miles data for 1970–2008 provided by Fearnleys.
2 Tonne-miles data for 1999–2013 as published in the Review of Maritime Transport 2013 by UNCTAD.
3 Tonnage data (dwt) for 1979–2013 as provided to us by UNCTAD.
For oil tankers and bulk carriers, the historical productivity is determined for the period 1970–2013, where
tonne-miles data from the two different sources had to be combined. As can be seen in Figure 38 and Figure
39, the productivities of the overlapping years match well.
For container ships and liquefied gas ships, the historical productivity is determined for the period 1999–2013.