Tony Abbott’s strategic embrace of a net overseas migration target may have prompted front-page splashes such as the odious “Shut the Door”, but the real-world consequences are likely to linger much longer for groups such as international students targeted by the push, demographers say.

The policy — to hack back net overseas migration (which goes by the delightful acronym NOM) from 300,000 to 170,000, or an annual rate of 1.4% — was announced by Abbott on Sunday despite net migration figures for 2009-10 already declining to 230,000-250,000, and private figures suggesting the figure will plunge to 175,000 by June next year and 145,000 by June 2012.

As of this morning, Australia has a population of 22,401,272, according to the ABS. In calendar year 2009, an extra 451,900 people arrived, a growth rate of about 2.1%. Of that increase, 66% were sheeted home to NOM with the remaining 34% sourced from births minus deaths.

But as Professor Graeme Hugo from the University of Adelaide told the ABC yesterday, half of that 300,000 are temporary visa holders, who will theoretically leave soon anyway. The remainder — 143,000 — is the actual permanent number that is 27,000 less than the target Abbott proposed.

And as numerous commentators have pointed out, that reduction from 300,000 is based on a 2008 change in how the ABS data is measured, so the comparison with previous years is immediately misleading.

Last night on The 7:30 Report, Abbott clarified that skilled visa applicants wouldn’t come under the spotlight, focusing the blast furnace by default on the 100,000-strong international students, many of whom are reaching the end of their time in Australia. The billion-strong industry has reacted angrily, with lobbyists and student groups claiming that the sector would be torn down by the plan.

Abbott was careful not to single out any specific group, suggesting instead that all target categories, whether they be 457 visas, skilled workers, international students or migrant families would be submitted to a white paper process in next year’s budget.

But demographers and big business have been relentless in their criticism of a specific headline-grabbing target. Experts contacted by Crikey said  the 170,000 figure would almost inevitably constrain policy choices when the needs of the economy change.

Curtin University Research Fellow Tod Jones said that it was “really difficult to put targets on these things” and that there should be a rolling policy debate to continually assess the nation’s labour needs.

“You need to ask what the economy’s doing. To commit to a target is to basically to say that you’re not looking at the demand for workers in different industries,” he said.

Jones said that the mining, trades and the service industry that could potentially see a spike in demand for labour: “Here in Western Australia, it’s hard to get a decent workforce, even in restaurants during boom times.”

Jones said the Abbott announcement was more to do with politics than considered policy: “It allows Abbott to reinforce his message that ‘we’re in control’ and that only the Liberal Party can control immigration. It steps away from the requirements, it’s all about the politics.”

Social demographer Mark McCrindle said politicians were limited in which parts of the system they could change, and that in a 1.4% growth rate, only 0.9% was subject to policy levers pulled from Canberra. A large proportion of the recent increase in NOM was caused by Australians stranded overseas during the global financial crisis returning home.

McCrindle said NOM had been gradually rising as a share of the total population increase, to the present 66%, from a previous split of closer to 50/50. But the government had limited options at its disposal.

“You can slash and burn and get to 170,000 arrivals but it will cause some pain in the export sectors into the international education sector … still with a little bit of pain it’s feasible to hit that number,” he said.

“The humanitarian program and asylum seekers are a very small part of the total, and there are limited amounts that can be done there. The student visa category is liable for rorting, so the government can potentially sort the out the humanitarian intake and tweak the student visas.”

But the fact remained that Australia was going to grow regardless of what the government did or didn’t do. “Population growth will take place regardless of any migration policy … we should start planning for growth caused by one new Canberra being added each year,” McCrindle said.

“Where’s the infrastructure, where’s the rail?”

But there are some other voices, particularly among the trade union community, that are keen to reduce migration, although not in the areas targeted by Abbott. Demographer Bob Kinnaird has been engaged by CFMEU national secretary John Sutton (a member of the Gillard government’s population panel) to look at the debate in the context of his members.

Sutton said he backed a “range” rather than a target: “You can’t pluck a number and say you’re going to hit 170,000, but Labor has talked a about a range of numbers, which is much more sensible.”

The government needed to urgently address the temporary worker situation, which, according to Sutton, were an overhang of policies put in place by the Liberals and prone to continued rorting. “There were a whole range of rorts and they were very popular with employers,” he said.

Speaking on Q&A last night, Malcolm Turnbull also seemed to back away from the preoccupation with targets, emphasising the Coalition’s plan to approach the Productivity Commission and claiming that immigration was part of Australia’s “DNA”.

“We’re a nation that’s been built on immigration, we just simply have to make sure that the rate of immigration is based on demand from our labour force,” Turnbull said.