We’ve become quite dependent on this huge inflow and outflow of temporary migrants, which far exceeds people coming on permanent visas. Businesses often want their temporary skilled workers to stay on.

The sale of education to overseas students has become one of our biggest exports, one on which our universities have become heavily dependent. Our hospitality industries rely on the casual employment of overseas students and backpackers. And farmers and country towns rely on backpackers for fruit picking and other unskilled work.

We’ve become quite dependent on this huge inflow and outflow of temporary migrants, which far exceeds people coming on permanent visas.

On top of all that, federal governments have become reliant on high migration to make our GDP growth figures look better. They often boast about how well our growth compares with the other rich countries, without ever mentioning that most of this is explained by our faster population growth.

And right now, of course, the economy’s growth is so weak we’d be in recession if not for the recent immigration surge.

All these are the reasons successive federal governments want to maintain strong immigration, despite the public’s longstanding reservations. Former prime minister John Howard did a great line in diverting the punters’ attention to resentment of some uninvited arrivals by boat, while he ushered in visa-wielding immigrants arriving by the plane load.

It’s only when high immigration becomes an issue before elections, as now, that the pollies make noises about slowing the inflow. It’s true that, since we reopened our borders following the lockdowns, our “net overseas migration”, people arriving minus people departing, but not counting those on brief visits, leapt to 528,000 in 2022-23, more than double what it was in 2018-19. And it may exceed another 400,000 in the financial year just ending.

This surge does seem to have contributed to the present acute shortage of rental accommodation and the big jump in rents, but Opposition Leader Peter Dutton is drawing a long bow in blaming the recent surge for the unaffordability of buying a home, which has been worsening for decades.

The telltale sign that Dutton is fudging is his plan to make more homes available by cutting the government’s permanent migration program from 185,000 a year to 140,000.

The government does control the size of this program, and often moves it up or down a bit, but the size of the program makes little difference to what matters most for the economy: annual net overseas migration.

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The trick is that about 65 per cent of the permanent visas go to people who are already here on temporary visas. Changing their visa status makes no difference to net overseas migration.

At times like this, the pollies would like you to think they have the power to move immigration up or down according to the economy’s needs at the time.

But they don’t. For the most part, the level of net migration is, as economists would say, “demand determined”. And, as the demographers will tell you, net migration tends to go up and down with the state of our economy.

When the economy’s booming, migrants are keen to come to Australia, and our employers are keen to have them, particularly if they have skills. What’s more, locals and former immigrants are more likely to want to stay here than go overseas.

It’s a different story when our economy’s weak. Employers are less keen to bring in people and migrants are less keen to come.

Now, our present circumstances don’t fit that long-established cyclical pattern. But that’s mainly because the economy’s been returning to normal after the end of the pandemic. This is particularly true of the people most disrupted by the pandemic, and who’ve done most to account for our recent downs and ups in net migration: overseas students.

Most students went back home during the lockdowns, but now many of them, and many newbies, are coming back in. We’ve had a lot more students than expected because, to encourage their return, the Morrison government removed the limit on how much paid work they could do. It took the Albanese government too long to wake up and end the concession.

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If you find it hard to believe the government has little control over the number of immigrants it lets in, note this. To be given a temporary visa, you have to fit one of the many categories the government wants: skilled, student, backpacker and so on. But there are no limits on the number of applicants accepted in each category.

Until now. Because it’s the students who’ve contributed most to the recent surge, the government is planning to impose caps on how many it will admit. The opposition is promising something similar.

Remember this, however. The economy is weak – and it is forecast to remain so for a year or two – so it’s reasonable to expect that, even without the caps on overseas students, net migration will fall back soon enough.

But an election is coming. Voters are unhappy about high migration and the high cost of housing, and both sides want to be seen doing something about it. How much the winner actually bothers to do after the election, may be a different matter.