In the third and last of his series about young people around the world as part of the BBC's Generation Next season, the BBC's Robin Lustig looks at how young people are learning to play an active role in political debate. Should more countries be allowing votes at 16?
You can marry before you can vote; you can join the army before you can drive a car. In many countries, the rules about precisely when you become an adult are nothing if not confusing.
Government minister Hazel Blears gets a youthful grilling
So, it's no surprise that many young people think it's high time they did something about it.
In Albania, for example, members of the country's youth parliament have successfully campaigned to raise the minimum drinking age from 16 to 18. They thought too many teenagers were getting drunk.
In the US, on the other hand, Alex Koroknay-Palicz of the National Youth Rights Association says he regards young Americans as an oppressed minority.
Young people are seen as "far more incompetent than they really are," he told us. "I think that if given the chance, young people are far more intelligent, far more responsible, and far more mature than we give them credit for.
"For thousands of years of human development, 15 or 16-year-olds have been considered as adults - but we treat them legally pretty much the same as a five-year-old or a six-year-old.
"If you're 13 and you kill somebody, they say: 'Oh, you're a responsible adult. We're going to throw you in jail for the rest of your life.' Whereas, if you're 13 and you want to vote, they say: 'Oh, you're a stupid little kid. You don't have any rights.' So they only seem to treat people as adults when they do something wrong."
In most countries, the legal age of majority is 18. That's when the law recognises that you are an adult - that you are entitled, in law, to have control over your own body, your decisions and your actions.
But that's not the same as what's called the age of licence, which is what you're allowed to do at any particular age: drink, marry, or drive a car, for example.
So, if you're not yet 18, but you want a chance to change things, what do you do?
In some countries, young people can be elected to become members of a youth parliament, where they can debate, lobby, and try to have an influence on the country's real, grown up parliament.
They don't yet have any real power, but they can learn what to do with it once they have got it.
Kate Parish, founder of the British youth parliament, says: "When they are first elected, a lot of them are unsure about what they're doing. A lot of them have never spoken in public before.
And then we see a real change - where once they wouldn't have said boo to a goose, all of a sudden they're standing up in front of an adult council meeting and saying: 'This is not acceptable! You might have closed our skate park down. What are you going to do about it?' It's a learning process for them."
And the chairman of the Albanian youth parliament, Endri Shabaney, says the adults in the national parliament would do well to learn from their younger counterparts.
"In the real parliament, there are fights. The members don't respect each other. But in the youth parliament, people respect each other. They are just discussing - nobody is going to be offended there. I think we young people are more responsible than the adults."
So perhaps more under-18s should be allowed to vote in national elections? In Iran, for example, you can vote at 15. In the Isle of Man, which isn't part of the United Kingdom and where they have their own parliament and make their own laws: they've just lowered the voting age to 16.
Cheers all round? Not quite. One teenage girl told us: "Basically, I don't know anything about what's happening. I haven't registered to vote and I haven't had any information."
Another girl said: "There's certainly a lack of knowledge and understanding. When the forms came round, I had no idea who was representing where I lived or what they were representing. I honestly didn't have a clue."
Psychologist Helen Haste at the University of Bath says under-18s are perfectly capable of making the sorts of decisions that could entitle them to vote.
"They can recognise that we are part of a community and that we have to work together as a group of people in a community, whether that community is a school, a village, a town or even a country. By mid-to-late adolescence, young people really can understand their obligations to the community."
Many young people do seem to be much more capable than adults are prepared to believe. Many are already playing an active role in influencing the decisions made in their community. So what will the world be like when they finally take over? No-one can be sure - but I'm looking forward to finding out.