Membership is obtained by purchasing, or inheriting a share ("toshiyori kabu") in the Association, of which there are 105. The value of these shares is extremely high and rules only permit them to be purchased by former sumo wrestlers who either reached at least a "san'yaku" rank ("komusubi" or higher) or been ranked for a significant number of tournaments as a "sekitori". Japanese citizenship is also required. Each share is associated with a particular name, and in the sumo world the former wrestler will be known by that name, usually with the suffix "oyakata". The members are also often called elders in English. An exception to the purchase requirement is made for the most successful former "yokozuna" who may be offered a one-time membership ("ichidai toshiyori") by the Association. Since this exception system has been in place, three former wrestlers, Taihō, Kitanoumi and Takanohana have obtained this status. A fourth, Chiyonofuji, was offered this status but preferred a normal share. These four all achieved more than twenty tournament championships in their active careers.