The English football league system, also known as the football pyramid, is a series of interconnected leagues for club football in England (although for historical, economic and financial reasons six Welsh clubs also compete). The system has a hierarchical format with promotion and relegation between leagues at different levels, allowing even the smallest club the possibility of ultimately rising to the very top of the system. There are more than 140 leagues, containing more than 480 divisions. The exact number of clubs varies from year to year as clubs join and leave leagues or fold altogether, but an estimated average of 15 clubs per division implies that more than 7,000 clubs are members of a league in the English football league system.