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The results of all port state control inspections are collected and evaluated with regard to the performance of flag states and classification societies. Regularly published in form of lists, these „rankings“ reveal to the public whether ships flying a certain flag or classed by a certain classification society are notorious for frequent deficiencies or have a more satisfactory record.
Each year these lists are newly established. The ranking is 
calculated by relating the number of detentions to the number of 
inspections over the previous three years.
Ranking of flag states and classification societies: „White list, Grey list, Black list and Performance list"
During many port state control inspections deficiencies of ships are discovered by the specially trained surveyors. Major deficiencies have to be rectified immediately. Occasionally port state control officers even have to detain a ship.The results of all port state control inspections are collected and evaluated with regard to the performance of flag states and classification societies. Regularly published in form of lists, these „rankings“ reveal to the public whether ships flying a certain flag or classed by a certain classification society are notorious for frequent deficiencies or have a more satisfactory record.
Ranking of flag states
The ranking of flag states is based on the following three different lists:
- The „White list“ contains only flag states of ships which have given , no or little cause for concern.
- The „Grey list“ contains flag states with an average performance.
- The „Black list“ contains flag states of ships which have shown an excessive number of ship safety deficiencies.
Ranking of classification societies
The ranking of classification societies is determined 
by the number of deficiencies which have caused detentions of ships and 
which could have been prevented with a correct survey by the responsible
 classification society. The ranking of classification societies is 
published with the annual "RO performance table" (RO = recognized 
organization) of the Paris MoU.
Implications of rankings
The rankings of a flag state and of a classification 
society have major implications for the inspection and the targeting of 
ships subjected to port state control. Ships flying the flag of a 
„blacklisted“ flag state and/or classed by a low ranking classification 
society are inspected more frequently and more thoroughly.
