AUSTRALIA's population just hit 22 million, according to the Australian Bureau of Statistics population clock.

The clock, based on population estimates taken from the Australian Demographic Statistics published in March, ticked over to 22 million at 1.58pm.

The ABS estimates Australia's population is bolstered by one birth every one minute and 44 seconds, and by a net gain of one international migrant every one minute and 53 seconds.

The swelled population estimates have come as a surprise to many who remember former treasurer Peter Costello's 2004 plea for women to go forth and give birth -- "one for mum, one for dad and one for the country."

Just four years ago, it seemed Australia was in the midst of a "baby drought".

Monash University demographer Bob Birrell said there had been a significant surge in the past year, both in the birth rate and in migration levels, "which most demographers have not anticipated".

"The fact that the national birth rate has gone up from 1.7 to 1.9 in the last four years is very significant," Dr Birrell said.

While the Howard government's baby bonus might have had some impact in raising the birth rate, he suggested a more likely explanation was the run of economic prosperity Australia enjoyed until last year's global financial meltdown.

"Until four or five years ago, the economic climate was such that you could not be certain if you could maintain a job or buy a house," he said.

While 249,000 babies were born in 2004, last year the ABS counted 297,000 births -- so significant an increase that Dr Birrell called it a "mini-baby boom". However, given the onset of the global recession, he said "we might struggle to maintain a birthrate of 1.9 now".

Melbourne mother Suzie Nader, 30, was thrilled to give birth to her second child, Noah, three days ago at Melbourne's Royal Women's Hospital.

Like many career women, Ms Nader said she deliberated before having her first child, but decided there was no point delaying her desire to have a family, given "there will never be a perfect time".

She said she had not ruled out having a third child -- "for the country" -- but planned to wait at least seven years before she made that decision.

Even more statistically significant is the rise in overseas migration.

Migration contributed 63per cent of last year's population growth of 2.1 per cent -- the highest growth rate since the 1950s and 60s.

On the other side of Melbourne, at Frankston on the Mornington Peninsula, South African migrants David and Lorraine Colvin are hoping to obtain permanent residency in Australia as soon as possible.

The couple decided to move to Melbourne after they were attacked in their home in South Africa by knife-wielding intruders. Now Mr Colvin has a job with a cable manufacturing company and they enjoy living in a city where they are not in perpetual fear for their safety.