Are you joking? We're the sixth largest country with a 52nd largest poplulation. 21 million is nothing, within my lifetime I expect us to top 100 million, we are one of the worlds more tolerant countries of migrants, we are peacefull and free making it a desirable place to raise a child, in terms of having the natural resources to support the country the only issue is really water and once we start recycling that problem will be dealt with, and any scientific body will tell you that we will have to sooner or later and heres the deal maker, we want to be important. Australians love to think of Australia as irrelevant and a country of Australia's population can't be, they can't raise a big enough GDP to be an economic power, even if we wanted it we would still struggle to be a military power due to the limmited number of able bodied personel that we could afford to commit to the military and really how else does one become a player?
Considering how organised our economy is and how resourcefull our land is the government would lick their lips at the idea of a 60 million man country, and really so would the people. Australia's covetted place on the world stage will come through population increase.