When did you consider yourself an adult?
They can drink, smoke, vote and get married, but many 21-year-olds still don't consider themselves to be adults.
There is increasing evidence that many young adults experience a "quarter-life crisis" between the ages of 18 to 25, according to Paul Jose, of Victoria University's School of Psychology.
"It's just taking young people a little bit longer to establish themselves as mature, responsible adults."
Dr Jose was responding to the findings of an Australian longitudinal study that indicated just 38 per cent of participants felt they had reached maturity with their 21st birthday.
The Brotherhood of St Laurence Life Chances Study traced more than 120 babies from their births in Melbourne in 1990, to their traditional "coming of age" in 2011. Thirteen per cent were adamant they did not feel like adults, while 49 per cent expressed ambivalence.
Dr Jose identified home ownership, marriage, parenthood and commitment to a career as hallmarks of the passage into adulthood, and said many of those milestones were put on hold by young people in favour of postgraduate study or travel.
"As a society, we're giving messages to young people that it's OK to be in this extended period of development, and it's forestalling the point at which they say to themselves, ‘I am an adult.'
"To a large extent, this is about self-definition, and it's very easy for a 21-year-old to think they're not an adult, because they're not married, they're living in their mum's basement and they've got a job at the video store."
Porirua Mayor Nick Leggett is clearly one who bucked the trend. He was the country's youngest mayor when elected at age 31. He was 27 when he bought a house and now runs a city, but the 32-year-old said he still felt young.
"People of my generation are not doing the life milestones necessarily in the same order as our parents.
"Values have changed a bit, so it doesn't really matter if you're not married - you don't feel like you're on the shelf if you're 32 and unattached."
Maturity was something that continued to grow with time. "I think you're always growing and learning at any age. Even if I was 80, I would hope that I would continue to grow."
Jami-Lee Ross, Parliament's youngest MP, began his political career at the age of 18, when he was elected to Manukau City Council. At 22, he was married and owned his first home.
He is now 26 and National's MP for Botany.
He acknowledged his path had been far from the norm. "A lot gets made about how it's good to have young people involved in government, and how we need a broad range of viewpoints around the table, and that's true.
"But the irony is, the majority of us who do get elected at a young age probably aren't that representative of the younger generation."
More typical of Generation Y is part-time student Fiona Ogilvie, 22.
"When I turned 21, I almost expected to wake up feeling different, but there was just a pretty dress in my wardrobe to wear to the party later."
Student Matthew Codd, 23, equated being an adult with "settling down and being responsible". Maturity should be assessed on a case-by-case basis, he said.
- The Dominion Post