IN this special Fairfax feature Shane Wright looks at the massive influx of growth into Australia’s capital cities.

They are the capital cities eating up the rest of Australia.

Already home to more than two-thirds of the nation's 25 million residents, each capital city will soon dominate their respective state or territory in a way that will challenge Australia's economic and political landscape.

Special projections from the Australian Bureau of Statistics show Melbourne, Sydney, Brisbane, Adelaide, Perth, Darwin and Hobart will soon account for at least half the population in each of their respective jurisdictions.

When Dorothea Mackellar wrote My Country, extolling "the wide brown land", in the first decade of the 20th century, about 40 per cent of the nation's 4.4 million residents lived in capital cities.

The most "centralised" state was South Australia where, by World War I, Adelaide accounted for half of the residents.

Since then, the capitals have absorbed more and more of their respective residents while a third of the 2500 towns that existed in Mackellar's time have disappeared - either abandoned or swallowed by nearby major cities.

Melbourne (76.9 per cent), Sydney (65.6 per cent), Perth (79.3 per cent) and Darwin (60.4 per cent) now account for well over half their state or territory's population.

By 2027, the bureau believes Brisbane will join the club in what has historically been the nation's most decentralised state. And by 2040, Hobart will be home to at least half of all Tasmanians.

Around that time at least 80 per cent of Victorians, West Australians and South Australians will be housed in their respective state capitals.

Despite its vast size, WA is the country's most centralised state, with 2.1 million of its 2.5 million residents living in Perth.

By the middle of the century, 85 of every 100 West Australians will live in the state capital.

At the same time Victoria is expected to have 10.2 million residents. Of those, 8.4 million are projected to be in Melbourne, making it the nation's largest city.

Grattan Institute chief executive John Daley says the dominance of the nation's capital cities is already changing the way Australians think about themselves.

He points out the cultural icons of the country are changing as more people live in the capitals and fewer are grounded in "traditional" rural Australia.

"Twenty years ago The Man from Snowy River was a cultural icon. Today it is MasterChef," he said.

"If you look at the MasterChef contestants, 12 of the 24 didn't have Caucasian parents. If you live in Sydney or Melbourne there's nothing strange about that, it's your lived experience. But if you're in country Australia it can look very different."

Mr Daley said trying to encourage businesses to move to regional areas rarely works, as firms had to overcome problems such as finding suitable staff or the cost of transport to important markets.

The institute's own studies have shown an effective "over-investment" in regional areas, suggesting political rather than economic interests drive many policy decisions.

According to Mr Daley, the growing dominance of the capitals will require more focus on the needs of urban Australians.

"We have been trying for 118 years to get people to move to the regions, and for 118 years we have had glorious failure," he said.

"People want to be where the jobs are, where their family is, where the services are.

"We haven't managed well the infrastructure of our major cities and that's what has to improve. Regional populations are relatively stable, so we shouldn't be overly worried about that."

Terry Rawnsley, a principal at SGS Economics and Planning, believes there needs to be an overhaul of the way Australia thinks about its regional areas, especially by federal politicians who cling to the idea of decentralisation.

Instead of establishing new industries on a whim, Mr Rawnsley argues policymakers should look at caring for those areas that simply won't grow.

"Some of these regions should be treated like a palliative care situation, whereby you keep the services in place for those people who remain, like Victoria's Wimmera," he said.

Fast train services that put larger regional centres within a two-hour trip of their capitals would enable the development of a European-style population pattern. Those regional centres could then focus on supplying essential services such as health and education to their hinterlands.

Centres outside of this network would have to focus on their own existing strengths, which are likely to be around mining (like WA's Karratha) or tourism (Cairns in Queensland).

"If you want to get people to the regions, look at Geelong or Gosford or the Gold Coast rather than to Armidale and making something out of nothing," Rawnsley said.

Politically, urban and rural Australia are already different worlds.

At the 2016 federal election, metropolitan Victorians voted 56-44 in favour of the Labor Party. Rural Victorians voted 55-45 in favour of the Coalition.

There were also sizeable political gaps between urban and rural Queenslanders, West Australians, Tasmanians and South Australians.

Only in NSW, where the state's northern and southern coastal areas provide substantial competition between the major parties, is there a relatively narrow difference between overall voting patterns in metropolitan and non-metropolitan areas.

Psephologist Kevin Bonham said the National Party and regional Liberals face the biggest risk from the demographic swing to the capital cities, as rural Australia loses more electorates.

The NSW seat of Hume, held by Morrison government frontbencher Angus Taylor, was once wholly confined to the Riverina, with its heart the city of Wagga Wagga.

Today, Hume has moved north to the point that it takes in the fast-growing south-western parts of Sydney. The new Western Sydney Airport will eventually run through a part of Hume, based on its current boundaries.

Dr Bonham said the recent Victorian state election highlighted the importance of Melbourne, where the surge in support for Daniel Andrews' government across the city's suburbs effectively decided the result.

"What happened in Victoria is an example of where Labor won the election in the city of Melbourne and the rest of the state was largely uninterested," he said.

Dr Bonham said the growing importance of Brisbane in a state that has historically been decentralised would throw up questions for both the Liberal and Labor parties.

"It's very difficult to balance that urban-rural blend with different messages. And in Queensland you have the Liberal National Party operating as a single party that puts tension between those messages," he said.

There's also a challenge around representation. The constitution locks in 12 senators for Tasmania, with the Apple Isle also guaranteed five lower house seats.

By 2040, the Bureau of Statistics expects the ACT will have more residents. But those residents will have less political say than their counterparts in Tasmania, with two senators and three members in the House, compared with 12 and five.

And with Victoria's population growing faster than the rest of the country, the number of MPs out of Melbourne will rival that of Sydney for the first time in almost a century.

Dorothea Mackellar had a strong interest in politics.

At the 1910 election, the year before the Australian publication of My Country, about a third of the nation's federal electorates were in state capitals - the political voice had a strong rural tinge.

At next year's election, 60 per cent of seats will be in our capitals.

Political and economic power is now firmly in the hands of those who call our major cities home.

The Age