The 1973 championship was cancelled due to safety concerns in Rhodesia/Zimbabwe
The 2020 championship was cancelled due to COVID restrictions.

The high figure (59 countries) in 2000 was due to the subsidised invitation of 28 countries to celebrate the millennium. It led directly to the creation of an African Championship.

A total of 111 countries have participated in at least one IODA World Championship
See "Best Ever" for details.