Why Treasury migration forecasts matter, and why they’re unconscionably high

Sure, at 25 million, already we've busted the 1998 ABS population forecast for 2051. But those extras didn't fall from the clouds like rain. Repeatedly, our sovereign government has accelerated net migration, counting GDP gains and largely discounting collateral costs.

Former Prime Minister John Howard and former Opposition Leader Kim Beazley were me-too high immigration men. The latter, during the mining boom, readily acquiesced to ballooning permanent migration and steeply rising 457 visas.

By way of thanks, the miners gelignited Prime Minister Kevin Rudd's 2010 tax on super-profits. Their boom damaged our overall competitiveness. In a Coalition phase pre GFC, and Labor-Coalition phase post GFC, we've hugely increased overseas student numbers and deregulated visa pathways. At cost to systemic quality and local aspirants.

So it's not that ABS couldn't do the maths. The government decisively upped the population momentum. Our average net migration over 2007-2017 - at 220,000 plus - considerably exceeds two multiples of the quarter-century net migration average up to 2006.

With overseas-student numbers possibly peaking, how could net migration ever top 270,000? One analyst has suggested this would rely on a strengthening economy, plus extra chip-ins from working holiday makers, visitors changing status, and the new temporary parent visa. Once again, so much for the spin, around migration and skills in demand.

On the other hand, net migration might slump, should the economy weaken. But we've trumped 170,000 net, every year since 2006. To bolster migration and 'jobs and growth', the government could speed up visa processing, tweak visa rules or categories, intensify student drives in Indiaor other markets, or unleash the migrant-parent visas.

Through to 2018-19, Australia trumpets '28 years of uninterrupted economic growth'. Surfing on net migration, the government and the Treasury may yet ballyhoo 30. Ordinary households and wage-earners would be left wondering, did they really 'burn' for us?

For the long term, the Treasury Intergenerational report assumes 215,000 annual net migration. Again, this is more than twice the average over 1982-2006.

Similarly, today's 'illustrative' ABS projections will admit of nothing but high migration, at levels of 175,000 (call this, lower high), 225,000 (medium high) or 275,000 (very high).

In effect, the Budget is adopting the 'very high' ABS option. The Plan, meanwhile, hews to the 'medium high' ABS option. Even under these assumptions, Australia's population would top 37 million, around 2050. By which time Sydney and Melbourne might hit 8 million.

To complete what is a less-than-virtuous circle, governments (notably their urban and transport planners) like to pretend that these brimming ABS numbers are 'independent' projections that will need to be accommodated.

Breaking ranks momentarily, even the NSW Premier briefly espoused a 'breather' of halving migration into NSW. She had a point. Once again, if you honestly want to 'bust congestion', you wouldn't start off with full-throttle migration, pouring into Sydney and Melbourne.