

But as patterns of migration to Sydney change, so have the names. There are now many suburbs where Nguyen, Li, Wang, Chan, Chen, Singh and Patel make a strong showing. Nguyen is concentrated in Sydney's south-west, while Lee dominates the Ryde-Eastwood area. Kim is king around Strathfield and Concord. The ethnic origin of some surnames is, of course, ambiguous: names such as Lee and Kim, for example. More than 30 different surnames claim the top ranking in at least one Sydney postcode - a number that rises to 80 across NSW. Only 36 names are ranked first in more than one NSW postcode.

Outside of the cities, names are much more Anglo-Celtic in origin. Kevin Dunn, dean of social science at Western Sydney University and a professor of human geography with a focus on immigration and urban studies, sounds a warning. "Any maps showing surname distribution suggest ethnic generalisations that are not there. They can mask the real strength of cities like Sydney: diversity in suburbs," he said. Professor Dunn said that Sydney has one of the most diverse settlement geographies in the world.

"In council areas like Woollahra, Waverley and Randwick the most common name is Smith. If we just look at this, it disguises the long-standing Jewish communities in the eastern suburbs," he said. A look at home ownership names in Waverley, for instance, shows that Cohen is the second-most-common name after Smith. That data comes from voomMAPS based on home ownership records. The data for postcodes is based mostly on landlines in the White Pages, with about 10 per cent of the data from mobile phones. However, not all mobile phone numbers are registered with Sensis, as some people wish to keep this number unlisted. While this is a more accurate measure of surname distribution than home ownership, it is important to remember that it is not 100 per cent accurate.

"Increasing numbers of people have no landline at all," Professor Dunn said. Despite this, he said that it is a reasonable method of representing surname distribution. Other methods, he said, would involve looking at births, deaths and marriages and other data. Professor Dunn said: "It's also important to remember that landlines have a smaller representation of ethnic diversity." Another indicator, but less reliable than the phone book, is land ownership. The map created by voomMAPS shows home ownership over the past two decades by local government region (pre-amalgamation). It shows Smith as the dominant surname across the city. But other names are present: Wang, Chen, Li, Lee, Singh, Patel and Nguyen.

Of course, not everyone owns where they live, so a map based on this would hide renters, who are likely to be less wealthy. So a look at such a map needs to keep this distortion in mind. For example, the old Marrickville local government area has Smith as the main home-owning name. This matches the phonebook for postcode 2203, but Nguyen is number two - and Nguyen is also number one in neighbouring postcode 2204. With the 2016 Census being conducted on Tuesday, surnames have been a bit of a touchy subject for some people. Critics of the Australian Bureau of Statistics' plan to retain surname information have said this is a real danger to people's privacy.