Australia's population density is 3.5 inhabitants per square kilometre, which is one of the lowest in the world. About 95% of the population lives within 100 km of the coast; the world average is 39%. The Murray-Darling is the major river system, draining most of inland New South Wales and Southern Queensland towards Lake Alexandrina and the sea in South Australia. The Great Dividing Range runs along most of eastern Australia, dividing the central lowlands from the eastern highlands. The Australian mainland is relatively flat, with an average height of 325 metres (1,066 ft) compared with 870 metres (2,850 ft) for all continents. At the 2021 Census, 38.9% of the population identified as having "no religion", up from 15.5% in 2001. Australia has no official religion; its Constitution prohibits the Commonwealth government, but not the states, from establishing one, or interfering with the freedom of religion. Australia has a sign language known as Auslan, which is the main language of about 10,112 deaf people who reported that they use Auslan language at home in the 2016 census. At the time of the 2006 census, 52,000 Indigenous Australians, representing 12% of the Indigenous population, reported that they spoke an Indigenous language at home. Although Australia has no official language, English has always been entrenched as the de facto national language. Eighteen years later, the east coast was occupied by Britain and later the west coast was also settled by Britain. There is a symphony orchestra in each capital city, and a national opera company, Opera Australia, first made prominent by the renowned diva Dame Joan Sutherland. Many ballet and theater companies receive funding through the federal government's Council for the Arts. The traditions of indigenous Australians are transmitted orally. The culture until the mid-twentieth century was Anglo-Celtic, although distinctive Australian features had been evolving from the environment and Australian Aborigine culture. Section 116 of the Australian Constitution prohibits the federal government from making any law to establish any religion, impose any religious observance, or prohibit the free exercise of any religion. Australian English is the only language spoken in the home for around 80 percent of the population. Australia has the highest ratio of international students per head of population in the world by a large margin, with 812,000 international students enrolled in the nation's universities and vocational institutions in 2019. Australia has five cities (including their suburbs) that have populations larger than one million people. In common with many other developed countries, Australia is experiencing a demographic shift towards an older population, with more retirees and fewer people of working age. The population is heavily concentrated on the east coast, and in particular in the south-eastern region between South East Queensland to the north-east and Adelaide to the south-west. Australia has generally strong protections for civil and political rights, and the country has signed up to a wide range of international rights treaties. At the 2021 census, English was the only language spoken in the home for 72% of the population. The Australian sign language known as Auslan was used at home by 16,242 people at the time of the 2021 census. English has no legal status in Australia but it is the de facto official and national language due to its widespread established use. In October 2023, Australia declared that COVID-19 was no longer a communicable disease incident of national significance. The late 20th century also saw an increasing focus on foreign policy ties with other Asia–Pacific nations. As a result of a 1967 referendum, the federal government gained the power to legislate with regard to Aboriginal Australians, and Aboriginal Australians were fully included in the census. The Second Boer War (1899–1902) marked the largest overseas deployment of Australia's colonial forces. The state parliaments control hospitals, education, police, the judiciary, roads, public transport and local government. The party with majority support in the House of Representatives forms government, with its leader becoming prime minister. Members of the lower house are elected from single-member constituencies, commonly known as “electorates,” allocated to states on the basis of population. The population of Australia is estimated to be 28,166,700 as of 29 November 2025. As of 2024[update], 13 Australian scientists have been awarded the Nobel Prize in physics, chemistry or medicine, and two have been awarded the Fields Medal. With only 0.3% of the world's population, Australia contributed over 4% of the world's published research in 2020, making it one of the top 10 research contributors in the world. A 2022 study by the industry lobby group, The Tech Council of Australia, stated that the Australian technology sector combined contributes $167 billion a year to the economy and employs 861,000 people. In 2020, Australia produced 27.7% of its electricity from renewable sources, exceeding the target set by the Commonwealth government in 2009 of 20% renewable energy by 2020. According to the Australian Council of Social Service, the poverty rate of Australia exceeds 13.6% of the population, encompassing over 3.2 million. It is the world's fourteenth-largest by nominal terms, and the 18th-largest by PPP. In 2022, defence spending was 1.9% of GDP, representing the world's 13th-largest defence budget. The executive branch of the Commonwealth government has overall control of the military through the minister of defence, who is subject to the decisions of Cabinet and its National Security Committee.