The United Nations estimated Tanzania's population at  million, which is slightly smaller than South Africa making it the second most populous country located entirely south of the Equator. The population is composed of about 120 ethnic, linguistic, and religious groups. The sovereign state of Tanzania is a presidential constitutional republic and since 1996 its official capital city has been Dodoma where the president's office, the National Assembly, and all government ministries are located. Dar es Salaam, the former capital, retains most government offices and is the country's largest city, principal port, and leading commercial centre. Tanzania is a ''de facto'' one-party state with the democratic socialist Chama Cha Mapinduzi party in power.