Documentation of statistics
Get an overview of the purpose, content and quality of the statistics. Here you can find information on the sources that the statistics are derived from, what the statistics contains and how often it is published.
Explaining the statistics
The data source is AIS data registered by the Danish Maritime Authority
The extract covers unique vessels per day that have identified itself as a freight or container vessel in the ship’s AIS transponder and have indicated than the vessel have been in port.
Danish AIS data also covers some ports in Western Sweden that lies within the reach of the Danish costal AIS receivers.
Ships that have identified itself as a different type of ship or have failed to register that it has been in port, will not enter the statistics.
Ships that entered a port one day and left the next will be included in the count on both days. Thus, the statistics is not to be considered port calls.
The graphics above shows the monthly development in port calls, average size of vessels per port call measured by gross tonnage (GT) and average freight weight per port call since 2000.
It shows that the reaction to the economic crisis in 2008 was to concentrate the reduced amount of freight on fewer vessels rather than sail the same number of vessels each with less freight or to make a shift towards smaller vessels. This change in the number port calls happened almost immediately since the fall starts in June 2008 which is the time of the onset of the crisis in Denmark. The number of port calls was in 2008 the best maritime indicator of the economic crisis that hit Denmark at the time.
Port calls in Danish ports are experimental statistics
Experimental statistics are statistics that are not considered a final form of statistics for various reasons. In the case of the harbour activity indicator , the statistics are considered experimental for several reasons:
- The statistics are based on substantial volumes of data from the AIS system, and the methods for processing data most efficiently and accurately are still evolving.
- The level of detail in the dissemination and the way in which the statistics are disseminated may change as Statistics Denmark receives feedback from users or, during the further development, finds another approach to be more expedient.
- Although several years of data has already been accumulated as a basis for the statistics, Statistics Denmark still wants a longer period of analysis and stability in the results, before the statistics are elevated to a permanent part of the statistics production.
Experimental statistics are published in spite of the above, because Statistics Denmark estimates that the relevant statistics contribute reliably to further information about the Danish community.
Read more about experimental statistics in the statistical documentation.
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