The ABC's temerity in hosting a debate about the merits of high population growth has drawn predictable ripostes from the economic establishment. Shades of the legendary note in the margin of a politician's speech: "shout here - argument weak".

There are at least four counts against the advocates of high immigration. First, their refusal to engage with the academic environmentalists arguing that we've exceeded the "carrying capacity" of our old and fragile land. Scientists? What would they know?

A bigger population requires a bigger government, with more debt. Nick Moir

Second, they keep asserting high immigration's great economic benefits, blithely ignoring the lack of evidence. Whenever the Productivity Commission has examined the issue carefully it's found only small net effects, one way or the other. Its latest modelling found only a "negligible" overall impact.

Third, the advocates not only decline to admit the high social and economic costs that go with high rates of immigration, they decline to accept their share of the tab, doing all they can to shift it to the young, the poor and those on the geographic outer, including many of the migrants.

You rarely hear pro-immigration economists acknowledging the clearest message economic theory gives us on the topic: more population requires more spending on additional public and private infrastructure if material living conditions aren't to deteriorate.

The more we invest in such "capital widening" to stop the ratio of capital to labour declining, the less scope for investment in "capital deepening" to keep the ratio increasing, and so improving the productivity of our labour.

When we fail to invest sufficiently in capital widening – which we have – the decline in living conditions is manifest in overcrowding, traffic congestion and long commuting times.

Why have we failed to invest sufficiently? Partly because a high proportion of the promoters of high immigration are also promoters of Smaller Government, never acknowledging the two are incompatible.

A bigger population requires a bigger government, with more debt, not less. When you persist with high population growth, but put the clamps on government, you end up with overcrowding, congestion and the rest.

Another truth the high immigration advocates refuse to acknowledge is that a much bigger population must lead to much bigger cities and higher-density living in those cities.

The Reserve Bank's estimates of the huge addition to Melbourne and Sydney house prices caused by state governments' acquiescence to resistance to higher density in inner and middle-ring suburbs, are partly a consequence of successful attempts to shift the spatial cost of high immigration onto the less well-placed.

The fourth criticism of high immigration is that it's the cheapest and nastiest way to pursue economic growth. You get a bigger economy, but not the promised benefits. The studies repeatedly fail to show high immigration leads to a significant increase in real income per person.

Of course, the business lobby has no reason to care whether high immigration yields economy-wide benefits. All they're after is a bigger domestic market, allowing them to sell more widgets, make a higher profit and justify a bigger salary package.

Few economists can see this is a cop-out. An escape hatch. As a way of achieving corporate growth, it's even easier than taking over your competitors. And it sure beats the hard graft of trying to increase profits by being more efficient and contributing to national productivity improvement.

As we've seen, high immigration probably comes at the expense of productivity-enhancing (capital-deepening) business investment and public infrastructure. To the extent that inadequate capital-widening leads to overcrowding and congestion, it worsens productivity.

In principle, one productivity-enhancing effect of high immigration is that you get greater human capital on the cheap by pinching it from other (mainly poor) countries.

After foreign students have come here and paid full freight for Australian qualifications, you let them stay and work. You select permanent immigrants on the basis of their skills, or you let skilled workers on temporary visas stay on.

But as Dr Bob Birrell, of the Australian Population Research Institute, has shown, there's a big gap between the claims made for our skilled migration program and the reality. We let in people whose skills aren't in high demand, and plenty of them end up driving taxis because the local professions' gatekeepers refuse to recognise their qualifications.

So it's not clear the benefits of our skill-pinching program exceed the cost of discouraging businesses from incurring bother and cost training enough of our own young people, when you can always get the government to let you bring in someone ready-trained.

High immigration may suit our rent-seeking business people, but it's a hell of a way to pursue the professed benefits of economic growth.

Ross Gittins is the Herald's economics editor.