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IPS173 Athanasios Petralias et al.
(SPC/SPV), including Management Fees and net Freight Earnings must be
calculated.
The estimation of shipping services revenues (exports of services) for each
vessel requires first identifying whether the vessel is hired, then estimating the
expected revenues, provided it is hired and allocating the amounts to the
respective counterpart countries. Since there is no direct information of
whether a vessel is hired, this can be indirectly inferred from its draft which is
available in the international databases. A draft above 20-30% of its max depth
signals the vessel holds cargo. Also, if there is port movement and the vessel
is not laid up or under repair, one can also assume the vessel is hired; note
that there are types of vessels (i.e. passenger, tugs) not relevant for draft. Then,
for each vessel hired, we calculate expected revenues by vessel type and size
(deadweight/TEU) using the respective, monthly Clarksons’ time charter rate.
Since rates are provided for specific deadweights/teu’s, we use linear
percentage differences, among two adjacent deadweight/teu categories, to
calculate each vessels’ revenues, based on the observed exact vessel’s
characteristics provided by commercial databases. The country of non-
resident is set to be the country of the last port visited, which is provided by
commercial databases. Although this might not be always exact, it is the best
possible proxy on basis of available information and it is aligned with the
statistical guidelines. To calculate Bunkers cost, it is first calculated the fuel
consumption of each vessel and then world bunker prices are used to
approximate the actual bunker expenses. Then, these are allocated to
counterpart countries on basis of the last port visited. Commercial databases
provide for each vessel the typical fuel consumption (in tonnes per day) at a
given (cruising) speed. However it is common practice for vessels to travel at
reduced speeds, for fuel economy purposes. There is a well-known theoretical
formulae, that links fuel consumption with the third power of speed (see for
example, Ronen, 2011). Given the consumption F0 at speed V0, fuel
consumption at speed V1 is equal to:

3
F1= F0(V1⁄0) ,
which can be directly calculated on basis of the variables that are available by
the commercial databases, as described above. Having calculated the actual
fuel consumption (in tonnes per day) by vessel, we rely on world bunker
indices to calculate the monthly fuel costs.
To calculate port expenses, first we find on basis of commercial databases,
the ports and canals wordwide most often visited by vessels included in the
registry. Then, we find the pricing policy of these ports, which is publicly
available (most of the times in their webpage). Main expenses include Berthing
(a fee when entering the port) and Dockage (a fee while staying in the dock).

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