The Convention prescribes minimum standards relating to training, certification and watchkeeping for seafarers which countries are obliged to meet or exceed; it does not deal with manning levels, IMO provisions in this area are covered by SOLAS. The Articles of the Convention include requirements relating to issues surrounding certification and to Port State Control (see below).  This is an especially important feature of the Convention in that it applies to ships of non-party States when visiting ports of States which are Parties to the Convention. Article X requires Parties to apply the control measures to ships of all flags to the extent necessary to ensure that no more favourable treatment is given to ships entitled to fly the flag of a State which is not a Party than is given to ships entitled to fly the flag of a State that is a Party. The difficulties which could arise for ships of States which are not Parties to the Convention is one reason why the Convention has received such wide acceptance. By December 2000, the STCW Convention had 135 Parties, representing 97.53 percent of world shipping tonnage. The word “watchkeeping” does not only apply to deck personnel but covers all departments including the engine room, radio department and proficiency with survival craft; there are special requirements for tankers.