I had a friend in college who was in a serious automobile accident that got into the newspaper. In the article, she was referred to as a woman. This was reasonable, as she was over 21 and living on her own, but it came as a surprise to her to be referred to as a woman and not a girl. (This would have been in the mid-1980s)
The age of physical maturation and the age at which people who are still in school consider themselves adults don’t coincide any more. I think people don’t think of themselves as adults until they believe they are old enough to be married. I remember a bit of shock at being in a wedding in college, looking at a relative, and instead of thinking “they are way too young to be getting married” as I had in the past when people my own age married, I thought, “Oh, goodness. She really is ready for this. She’s old enough. I am old enough!!” That released a bit of an inner “eeek!” let me tell you. (Thinking back, I would have been about 23 or 24 at the time.)
It astonished my husband and me to know how many high school students our sons’ age were not interested in getting a driver’s license. Those of us who are older remember when most people that age could not wait to get a driver’s license. Being able to drive isn’t the signal of independence and adulthood that it once was. Maybe it is because nobody can actually work on their own cars any more, I don’t know. Maybe it is because parents can keep their children under surveillance at all times now, if they want to do that. Maybe it is because the age at which marriage is considered a rational possibility is pushed out to the date of a family-supporting level employment, which seems like a day which is not even guaranteed to come at all! It does seem clear, though, that people are pushing the age at which they consider themselves adults later and later in life. When the day does come, they seem to feel they are pretending a role rather than traveling through a certain phase of life that was certain to come, ready or not.