Melbourne is officially Australia’s biggest city after overtaking Sydney ‘on a technicality’

Data suggests Melbourne has nearly 19,000 more citizens than Sydney

Melbourne is become Australia’s most populous city (Getty Images)

Melbourne has overtaken Sydney to become Australia's most populous city for the first time in over 100 years due to a boundary change.

Melbourne now has 18,700 more citizens than Sydney, according to official statistics

Melbourne surpassed Sydney to become the most populous city after the Australian Bureau of Statistics (ABS) added a new district, expanding the city limits, in order to accommodate the rising population.

According to data from June 2021, Melbourne was home to 4,875,400 people following the inclusion of Melton. The population of the Melton region reportedly grew by 61 per cent between 2011 and 2021.

“The 2021 census told us that Melton and the rest of Greater Melbourne was now, statistically, one contiguous area,” ABS regional population unit demographer Andrew Howe told the Sydney Morning Herald.

“Until the 2021 census definition, the Sydney significant area had a higher population than Melbourne.

“However, with the amalgamation of Melton into Melbourne in the latest significant urban area classification, Melbourne has more people than Sydney – and has had since 2018.”

Melbourne would have first surpassed Syndey's population in 2018 when comparing the two cities using the updated boundaries.

The ABS uses several methods to calculate the urban population, including the 'significant urban area classification', which captures urban centre populations as all adjoining centres with more than 10,000 people.

When calculated using the traditional 'greater capital city' metric, Sydney was still ahead by a margin of 283,600 in 2021.

The "functional areas of city", which include populations who frequent or work within the city, but may live surrounding it are taken into account in the traditional method.

Melbourne is expected to overtake its northern rival around 2031-32 when using that measure.

Melbourne, which has been growing rapidly outpacing Sydney due to multiple patterns of migration, was ranked as Australia’s most liveable city and 10th in the world by the Economist Intelligence Unit’s Global Liveability Index for 2022.

Macquarie University demographer Professor Nick Parr told the Australian newspaper that the main reason for Melbourne’s faster growth is the difference in net internal migration.

“Sydney’s growth has been slowed by its substantial net losses of people due to internal migration,” he said.

“Far more people have moved out of Sydney going to other parts of Australia, especially to the rest of New South Wales, Queensland and Victoria, than have moved to Sydney from elsewhere in Australia.”