The premier conference that is organized by the World Petroleum Council is called the World Petroleum Congress. Starting in 1933, the congress was held every four years until 1991, with a 14-year hiatus in between 1937 and 1951 because of World War II. After 1991, it was held every three years until the year 2000. There was a move to have it hosted every two years after the 2000 edition, with Rio de Janeiro hosting one in 2002, but the cycle returned to every three years after that. In order to host a congress, there is a bidding process by interested cities for one in a particular year.