Non-Adults: The Future

In other words: infancy, childhood, and youth
I see why

There are various terms and categories for non-adults: newborn/neonate, infant, child, pre-teen, teenager, adolescent, youth. There are biological criteria, and legal criteria. Legally, a youth is defined as 15-24, for the U.N. An adult in many countries, including the U.S., however, is 18. An infant is less than one year old, or unable to walk. A newborn, or neonate, is less than 1 month old. Then there are toddlers and pre-schoolers. The other pre is pre-teens. A teen would obviously be 13 to 19.

None of this is really that relevant for me. I basically would say if you are not adult, you are youth. The definition of adulthood varies from country to country. I, being American, will just say 18. Or, as Chef on South Park says, the time to have sex is 17.

So, if I want to find out the current youth population, I should know how many are under 18. Or I could use the U.N. definition and look up the demography age 24 or younger. Using this scheme, I could try to do an age breakdown on children (0-14), and youth (15-24). Children include infants, toddlers, preschoolers, and everyone else under age 15, like preteens and early teens. I think 13 and 14 year olds are teenagers. They are, right? Anyway,

Now, we have 6.7B (specifically, 6.6579B, according to the U.S. census bureau) people.
http://www.census.gov/ipc/www/popclockworld.html

In 1985, the world population was 4.854B. So, 1.8039B people have been added to the world, net, more or less, since 1985. The oldest of the '85 cohort would be 23 by now, which is still in the U.N. youth category. (The world "youth" population (age 19 or less) was 1.744B, then). That leaves it fuzzy. How many of us died since '85, and how many were born (still living) in '84? There's infant mortality and mortality, in general, to take into account. But to do the calculation anyway, using the same number of youth, I could guesstulate that they make up about 27 percent of the world.

I couldn't find any good global youth-percentage statistics on the net.
Although,
1. I did find this 1985 global population chart, if however less-than-perfect (we should have a graph, and more current at that):
http://www.cimt.plymouth.ac.uk/resources/data/worldpop.htm
And
2. Aha! This is not a graph, but it's better (click on the bottom of the page).
http://www.census.gov/ipc/www/idb/worldpopinfo.html

Actually, that was weird that I came up with 27%, because I just found this fact on Wikipedia: According to the 2006 CIA World Factbook, around 27% of the world's population is below 15 years of age. If you add the eight more years the U.N. defines as youth, the under 25 year olds make up a pretty good chunk of total world population.

The conspiratorial might say they chose the age 15, to generate that percentage, or that I am controlled by the cia, lol.

Anyway, let's see what that percentage is. I did the math with the U.S. (global) census data. 2.41B people are 19 or under. And almost 3B are under 25. Specifically (and to the person!), the percentage of youth (under 25) on earth IS (drumroll please) about 44.915%. That's 2,999,238,077 divided by 6,677,563,921 (!).

In any case, youth will be the leaders of tomorrow. Or they can be the leaders of today, in fact.
See http://en.wikipedia.org/wiki/Luke_Ravenstahl (He became a U.S. mayor at age 26, after gaining a seat on Pittsburg's city council at age 23). You've got to enjoy your youth, though, if you can. People can be so serious. Even dour.

Youth (maybe you're young at heart?) can either join existing leadership structures, or form new ones. Here is the CIA factbook link on every current political party and leader in the world today (3/08). Youth, if you don't form your own parties, make your voices heard to the existing ones. Empower thyself. Have a party!
https://www.cia.gov/library/publications/the-world-factbook/fields/2118.html