It is uncommon for just two cities to account for such a big share of a nation’s population and output.
Even when Australia is compared with other highly urbanised countries the relative size of our two largest urban centres sets us apart.
Canada’s two biggest cities – Toronto and Montreal – are both significantly smaller than Sydney or Melbourne and together only make up about 28 per cent of the population.
In Britain fewer than 20 per cent live in the two biggest cities, London and Birmingham, while Japan’s two biggest urban centres, Tokyo and Yokohama, account for less than 10 per cent of the total population.
Melbourne and Sydney are often cast as rivals but the cities have much in common.