By Pallavi Singhal
Sydney's western suburbs are among its youngest, and a number of north shore postcodes are the oldest, as people aged 65 and older outnumber those under the age of 15 in much of NSW.
Auburn is Sydney's youngest suburb, with a median age of 32.3 years. Strathfield and Sydney follow closely with a median age of 32.9 years, and Blacktown has a slightly higher median of 33.2 years.
Blacktown also has one of the highest percentages of young people, with 22.9 per cent of its population under the age of 15.
Camden, in Sydney's south-west, has the highest proportion of people under 15 with 23.7 per cent of its residents falling in that age group.
Auburn youngster Emily Gessner.
At the other end of the spectrum, Pittwater is one of Sydney's oldest districts, with a median age of 42.9 and 18.6 per cent of its population aged 65 and older.
Blue Mountains has a slightly higher median age of 43.5, and Ku-ring-gai has a median age of 41.7. Mosman is next with a median age of 41.2 and Hunters Hill has a median age of 40.4 to make up the top five oldest suburbs.
"Younger populations living in western Sydney is the result of people in their late 20s and 30s moving into this area and having children," a spokesperson for the Department of Planning and Environment said.
The growth in the number of people aged 65 and older has more than doubled the growth in those aged under 15 across metropolitan Sydney in the 10 years to 2025.
Metropolitan Sydney is now one of only two regions in NSW, along with the central west and Orana, where the number of people under the age of 15 is greater than those aged 65 and older.
People in this oldest age group now outnumber those in the youngest in NSW's Central Coast, Hunter, Illawarra-Shoalhaven, North Coast, and South East and Tablelands regions.
"The older age profiles in the northern suburbs of Sydney reflect where people were choosing to live when they began families 40 or more years ago."
Several districts in NSW are now older than Japan, which has one of the most rapidly ageing populations in the world. Great Lakes on NSW's mid north coast, with a median age of 54.7 and a 33.5 per cent of its residents aged 65 and older, is significantly older than Japan, which has a median age of 46.9 and more than a quarter of its population aged 65 and older.The state's five oldest postcodes, Great Lakes, Eurobodalla, Urana, Tenterfield and Gloucester, all have a median age over 51 and between one-quarter and one-third of all residents in the oldest age group.
"These different rates of growth between the older and youngest age groups are transforming populations in a way never before seen in Australia," according to the Department of Planning and Environment.
The government is tailoring its regional plans to the different age mixes in various areas to ensure the provision of more "child-focused services" or "services and infrastructure for older people" as needed.