The Sustainable Population Australia website states that the optimum population for Australia is 10 million at the current standard of living (as determined by the WWF's Living Planet Report 2002). At a lower standard of living, it could be up to 21 million. (Numbers in the quote were taken from the UK-based Optimum Population Trust.)
Well, we have now surpassed 21 million people in Australia.
According to the Australian Bureau of Statistics, "On 25 January 2008 at 11:29:05 (Canberra time), the resident population of Australia is projected to be:
This projection is based on the estimated resident population at 30 June 2007 and assumes growth since then of:
one birth every 1 minute and 56 seconds,
one death every 3 minutes and 58 seconds,
a net gain of one international migrant every 3 minutes and 5 seconds leading to an overall total population increase of one person every 1 minutes and 42 seconds.
The Australian Bureau of Statistics tells us that, "The annual population growth rate for the year ended 30 June 2007 at 1.53% was the highest annual growth rate for a year ended 30 June since 1989. [...] 56 per cent of the population increase in Australia was due to immigration, which reached 177,600 persons in the financial year up to June 2007."
According to the same Australian Bureau of Statistics website, "For the 12 months ended 30 June 2007, Australia's population growth rate (1.5%) was higher than that of the world (1.2%). Australia's growth rate was lower than that of Papua New Guinea (2.2%), Malaysia (1.8%), and India (1.6%). It was higher than Singapore (1.4%), Indonesia (1.2%), New Zealand (1.0%), Canada (0.9%), United States of America (0.9%), Thailand (0.7%), China (0.6%), Hong Kong (0.6%) and the United Kingdom (0.3%). Unlike Australia, Germany experienced no change. Further, Japan experienced a decrease in population (0.1%)."