Emerging Adults

At what age do you become an "adult"? 18? 21?
A new survey by Clark University in Worcester, Massachusetts, revealed that there may be gradations of adulthood.
Witness the advent of "emerging adults" (age 18 to 29):

Jeffrey Jensen Arnett, a research professor in psychology at Clark University, coined the term as a phase of human development for the period of late teens through the 20s. It began with Gen X (born in the mid-'60s through early 1980s) and has rippled through to the next generation, the Millennials.
The main contributing social forces are later ages for career, marriage and parenthood, says Arnett, who has been studying young people for 20 years. [...]
To feel more like a grown-up, Alana Prant, 23, says she wants to become financially independent. That's the response of 30% of those surveyed who said financial independence is the most important factor in becoming an adult.
"I'm about to be 24. I should feel like an adult, but I don't," she says. "My parents completely support me."

Sharon Jayson of USA Today explains: here