Papua New Guinea is a country in Oceania, occupying the eastern half of the island New Guinea and numerous offshore islands. Papua New Guinea borders the Coral Sea, the Southern Pacific Ocean, and Indonesia. The country’s geography is diverse. A spine of mountains, the New Guinea Highlands, runs the length of the island forming a region covered with dense rainforests. The government system is a constitutional parliamentary democracy and a Commonwealth realm; the chief of state is the queen of the United Kingdom, and the head of government is the prime minister. Although much of the population relies on subsistence farming, Papua New Guinea has a mixed economy in which a lack of a market economy has resulted in state monopolies in some sectors of the economy. Papua New Guinea is a member of the Asia-Pacific Economic Cooperation (APEC).