I'm one of the ones that said I would consider anyone under 30 to be "today's youth". This is based on the fact that many, many people in that age range have not come close to achieving the levels of maturity and responsibility you described having had at that age. In my workplace not one single one of the employees in their 20's are married and for many of them it's their first "real" job.
This was basically my response. I believe early 20s should be the cutoff, but in practice I would now say 30ish.
Like the PP, my husband and I were extremely independent so we would definitely have been considered "adults" before age 25. We had children, we owned a home, we both had careers. Even as teenagers we were doing things that some adults struggle with (ex. I did my parents' taxes myself when I was in HS and college so that I could file my own FAFSA).
Virtually all of the "young people" I know now have their parents supporting or helping them in some fashion. Every married couple I know under 30 still has their parents pay for some of their bills (cell phone, auto insurance, student loans, etc). Perhaps they're just doing it to be nice, but I really feel like if you're mature enough to get married, have children, whatever, then you should be able to shoulder the responsibility.
In the US would say like 16-30. I'm 48. "Youth(s)" strikes me as the space between children and adults. Interestingly I think I would have put the upper end lower maybe10 years ago--I think I might have put it as lows as 24 or even 22. I suppose it must just be that I'm older, but it doesn't seem that way--I really feel like today's twenty-somethings are just different than in the past...
I don't think there's anything different about them as people, I just think that parenting and societal expectations have changed.
Our oldest child is 20 and she has lived completely independently for the last year. (And even before that we did not pay for any expenses other than schooling and health care.) Even when I say that she pays for everything and lives on her own, people still assume that we must pay for some of her bills. I can't tell you how many times I have received a "Wait, you don't even pay for her cell phone? Or her car insurance? Or her...?" Nope. She even pays for her own medical copays and prescriptions (she is on our insurance but we have a family plan so there's no additional cost).
I think this is because for all the under-30s that we know (including the married ones that I mentioned above), they believe that they are "independent adults" even thought their parents are still supporting them in some way. So the expectation is that's the norm and that everyone who is an independent adult must have some support from their parents.
Slightly OT, but I know someone is going to be offended by my post. I'm not judging parents helping their kids and I have no issue with doing nice things for your children (putting a big chunk toward their student loans, helping them with a car, paying for a vacation, etc). I just believe that it's important for them to learn the skills necessary to being an adult (budgeting, paying their own bills, etc.) It's hard for someone to learn how to live within their means when they don't have an accurate picture of what their "means" are.