I have to question this population is great assumption.
The rate of growth in the human herd is unsustainable. If the current exponential rate of growth continues we will get to a tipping point where our demand on resources is greater than the supply, then things will get very ugly.
Melbourne and Sydney's liveability has gone down hugely imo. I live in Melbourne and the place is now bursting at the seams, sometimes it's so crowded you can't get on a train. Traffic horrendous.
Letting in all these immigrants in a largely arid country is f'ing stupid imo. May benefit big business and existing property holders (while screwing our kids - I'm glad I'm not finishing uni now, with massive debt and highest graduate unemployment rates in the series!! And massively expensive housing).
