CLARIFICATION
continued (4)
Sources
The contents of the
database
Definition of
'Rotterdam'
The definition of
international transports
Weights
The reliability of
the statistics
The
(re)classification of cargoes
Registering and
classification of bunker material
Other main
(re)classification issues
Notes
Definition
of 'Rotterdam'
The main sheets only contain data on throughput
within the port area belonging to the municipality of Rotterdam. As the
port expanded spatially, smaller ports were sometimes integrated in the
official Rotterdam statistics. In the case of Pernis and
Vondelingenplaat, included in the Rotterdam data since 1934, we have
made a separate file for sea borne and inland shipping cargo flows to
and from this area for the period 1925-1933 (earlier data are not
available). It should be noted that 'Hoek van Holland' traffic is not
included in the data on sea-borne traffic after the Second World War,
although this place was part of Rotterdam.
The throughput in the other ports along the New Waterway was not
insignificant compared to Rotterdam, in particular in handling of bulk
products and homogenous break-bulk flows like wood. Restricting a
comparison of the development of cargo flows in Rotterdam with major
ports in the Hamburg-Le Havre range to the official Rotterdam data
could lead to misleading conclusions. Therefore, we have included extra
sheets on sea-borne throughput in all ports along the New Waterway. The
New Waterway ports are: Hoek van Holland, Maassluis, Schiedam (from
1925), Vlaardingen, Pernis and Vondelingenplaat (from 1925 until 1934;
included in Rotterdam from 1934), Rotterdam, Zwijndrecht (from 1925)
and Dordrecht (the latter two ports are strictly speaking not located
along the New Waterway, but they are usually considered part of the
'Rijnmond' port area; Dordrecht became of serious importance since 1930
when a special 'seaport' was opened). The interbellum data are
compatible with the Rotterdam data in the main sheets and consist of
totals only for reference years 1920, 1925, 1930, 1935 and 1938/1939
and easy accessible data for 1927-1929 and 1931-1934 plus some more
specific information on Vlaardingen.7
In particular due to the dry bulk handling firm Havenbedrijf
Vlaardingen-Oost that was founded by German iron and steel firm August
Thyssen in 1920, Vlaardingen developed into a port that had to be taken
seriously. On average, HVO handled 2,3 million tons per years between
1920 and 1939 and 2,9 millions tons between 1946 and 1968.8 Except statistical
registration, this company was in all senses part of the port of
Rotterdam. To indicate the relevance of the Vlaardingen performance in
ore handling in particular, we have included the sea-borne throughput
of iron and manganese ore in this port between 1920 and 1939 (this
compares to the data on 'iron ore' in the main sheets).
For the period 1946-1980, easy accessible information is available for
sea-borne throughput in the New Waterway ports for major categories.
The data are taken from the same source as the main sheets, but from
other tables.9
The Rotterdam data are included here to compare them with New Waterway
data that are apparently assessed following the same methodology. It
should be noted that the Rotterdam data included in this sheet are not
the same as the Rotterdam data in the main sheets, although the totals
are nearly identical in incoming traffic in almost all years before the
1970s and in outgoing traffic between 1946-1966. The totals are
calculated. Major differences between totals mentioned in the source
and totals calculated occur in outgoing Rotterdam traffic in 1954-1955.
The data on mineral oils are clearly mistaken in these two years; they
are much too low compared to the data in the main sheets. But the
amounts of other categories, in particular 'other goods', are seriously
wrong too. Therefore, for 1954-1955 the data on outgoing and total
Rotterdam traffic are not included in the sheet. The categorization is
not according to the NSTR. The amounts of cargo mentioned in the New
Waterway ports/Rotterdam-categories are (almost) identical with those
of corresponding NSTR-categories in main sheets of the database in the
case of mineral oils and coal, but for other categories only for
restricted periods, i.e. ore (incoming 1946-1952, outgoing 1946-1950),
fertilizers (outgoing 1946-1953 and 1956-1966) and wood (outgoing
1946-1953).
The
definition of international transports
The statistics do not contain imports and exports to and from the
Netherlands' partners in the Benelux, Belgium and Luxemburg, between
1971 and 1985. However, transit traffic to and from these countries
through Rotterdam is included in these years.
Weights
The sources yield time-series expressed in kilograms or -after World
War II- tons (1 ton = 1.000 kilograms). All data in the database were
converted to tons. The time-series used were initially partly expressed
in net weights. However from 1917 onwards, all data in the database are
in gross weights.10
These "gross" weights consist of the weight of the commodity including
packing.11
Transport devices or secondary package such as tanks, lorries and
containers are not included 12,
unless the transportation firm (instead of customs) stated the weight.
In the latter case CBS included secondary packing and calculated the
so-called "grossplus weights".13
Probably, the data on rail transport since 1971 are gross plus weights.