|When is IAAF World Championships?|
|What is IAAF World Championships?|
The International Association of Athletics Federations (IAAF) hosts the championships for track and field every two years. Founded in 1983, the biennial event was originally held every four years but was changed to every two years in 1991. The IAAF World Championships has grown from 1,300 competitors from 154 countries in 1983 to over 2,000 athletes from over 200 countries.
Since the first IAAF World Championships, the most successful countries have been the United States (275 medals), Russia (151 medals), and Kenya (100 medals).