Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country in Oceania and the world's sixth-largest country by total area. Its population of nearly 26 million is highly urbanised and heavily concentrated on the eastern seaboard. Australia's capital is Canberra, and its largest city is Sydney. The country's other major metropolitan areas are Melbourne, Brisbane, Perth, and Adelaide. Australia is a developed country, with the world's thirteenth-largest economy and tenth-highest per capita income. It is considered a regional power and has the world's thirteenth-highest military expenditure. Immigrants account for 30% of the population, the highest proportion in any country with a population over 10 million. The country ranks highly in measures of health, education, economic freedom, and civil liberties.