Australia's population reached 22,546,300 people at the end of March 2011, growing by 312,400 people over the year.

According to preliminary figures released on Thursday by the Australian Bureau of Statistics (ABS), annual population growth rate slowed to 1.4 per cent for the year ending March 2011.

This is equal to the average annual population growth rate for the past 30 years and is down from a peak growth rate of 2.2 per cent in the year ending March 2009. It is also the lowest growth since the year ending March 2006 when an increase of 299,269 people was recorded.

Net overseas migration accounted for 54 per cent of the growth for the year ending March 2011, with the remaining 46 per cent due to natural increase, or births minus deaths. Net overseas migration continued to decline to the end of March 2011.

At 167,100 people, the preliminary net overseas migration estimate for the year ending March 2011 was 24 per cent lower than the 220,000 people for March 2010.

Natural increase for the year ending March 2011 declined by 9,400 people when compared to the previous year. This is due to a 4 per cent increase in the number of registered deaths, at 146,600 people, and a 1 per cent decrease in the number of registered births, at 291,800.

Western Australia continued to record the fastest population growth rate at 2.2 per cent, while the Northern Territory recorded the slowest growth rate at 0.4 per cent.