How many versions of Mahjong are there?

There are many, many variations of Mahjong. In China alone, there are said to be over 30 variants. These variants tend to be regional. However, some variations have been standardized by the creation of a governing body. For example, The National Mah Jongg League standardized Amerian Mah Jongg in 1937. The World Mahjong Organization is the international governing body of the variation known as MCR (Mahjong Competition Rules). This organization was established in 2006, with its headquarters located in Beijing, China.