The 470 World Championships have been held every year since 1970 and organised by the International 470 Class Association and recognized by the International Sailing Federation. When the Championship forms part of the ISAF Sailing World Championships the ISAF also organise the event. The 470 is a sailboat class used as equipment for the Olympic Sailing Competition.
Under 21 'Open' Junior World Championships
Initially the Junior Worlds also didn't permit competitors who had been selected for World or European Championships.
References
470 World Championships Wikipedia(Text) CC BY-SA