A population boom is helping Sydney cement its status as one of the world's most multicultural centres, but the remainder of NSW is much less diverse.  The trend is expected to be one of the key highlights captured by the August 9 Census, which collects fresh data about where people are born and the languages they speak to help paint a picture of who makes up the state and nation.  The Australian Bureau of Statistics expects the Census will confirm Sydney's population has cracked the five million mark, after increasing by more than the entire population of Tasmania since the last Census five years ago.  The 2011 Census uncovered a gradual increase in the number of people born outside Australia living in Sydney as well as a rise in the number of bilingual or multilingual homes.  About 40 per cent of the city's population was born overseas - well above the national average of 28 per cent.  In regional and rural areas of NSW only 16 per cent of people were born overseas.  "We are increasingly a multicultural society and a five-yearly Census is really important to know how we live and how we are changing," ABS NSW director Liz Bolzan said.  The 2011 Census revealed Blacktown, in Sydney's west, topped the country as the suburb with the largest number of migrants, originating from 142 countries.  Randwick, in Sydney's east, came in second with 138 represented countries.  Southwest Sydney has been at the centre of Sydney's population boom in recent years, with Cobbity-Leppington expanding by 26 per cent between 2014 and 2015.  Demographer Mark McCrindle expects the Census to show Sydney's population boom is continuing.  "We'll see steady growth of those numbers," he said.  The 2016 Census is being carried out online for the first time this year. Results are expected to be released in April 2017.
Sydney is looking likely to become one of the multicultural centres of the world after a population boom, while regional NSW will remain largely unchanged.