Laos is a single-party socialist republic. The capital city is Vientiane. Other large cities include Luang Prabang, Savannakhet, and Pakse. The official language is Lao. Laos is a multiethnic country with the politically and culturally dominant Lao people making up approximately sixty percent of the population, mostly in the lowlands. Various Mon-Khmer groups, the Hmong, and other indigenous hill tribes, accounting for forty percent of the population, live in the foothills and mountains. Laos' "strategy for development is based on generating electricity from its rivers and selling the power to its neighbours", namely Thailand, China, and Vietnam. Its economy is accelerating rapidly with the demands for its metals. It is a member of the Asia-Pacific Trade Agreement (APTA), Association of Southeast Asian Nations (ASEAN), East Asia Summit and La Francophonie. Laos applied for membership of the World Trade Organization (WTO) in 1997, and on February 2, 2013 it was granted full membership.