Responding to a bunch of thoughts here. Well too lazy to quote.
WA - I guess this is your technically first "sex" topic. But hey all your topics have been "relationship/sexuality" oriented. Why so curious about this stuff? Should you not be enjoying the fascinating world of carbon compounds instead?
A lot of people assume that teenage pregnancy or babies having babies is a "western" phenomenon. Such practices are very prevalent in rural parts across the world where kids are married off and expected to start families by the time they hit puberty. The way I perceive it, teenage pregnancy is not an issue of modernization, freedom or of conservatism, old fashioned traditionalism. This is the result solely of "ignorance". Some extreme traditionalists are ignorant of the importance of maturity and expect kids to start shouldering family responsibilities at a young age. Some extreme modernists are ignorant of the importance of responsibility and end up committing actions they cannot be accountable for. Societies need to balance the two extremes.
Here is a chart based on UNICEF's ranking of teenage pregnancies in developed nations. http://www.nationmaster.com/graph/peo_tee_bir_rat-people-teenage-birth-rate
(Note: This study does not include nations where teen marriage prevails in society)
Surprisingly France, Belgium, Sweden, Norway, Germany, Netherlands, Spain - the usual suspects have it very low compared to USA and UK. These are countries where condoms are available in vending machines, age of consent averages 14. UK & US have severely criticized Japan for its po*nographic promotion through adult animation, yet even Japan scores amidst the lowest in teen pregnancy. The problem lies not in "westernization" but social structure related to "sexuality".
A variety of factors make the difference. I wont go into too many details but mostly aspects like glamorization of child birth, lack of parental responsibility, lack of social and family structure, faux openness of sex - where it exists in media - but the family really does not touch it with their kids - creating conflicted and ignorant children.
Parental responsibility is the key. The thing is when the right people have kids they will raise them right and responsibly. They know when to have which talk. It comes naturally to responsible parents. With good parents you do not have to worry about the right age, the parents instinctively know based on their childs school, and social surroundings to know when the child will need the talk. If you raise your children right, they will make the right decisons no matter what media, society or values the world exposes to them. That requires a lot of heart and soul into parenting and waiting till you are ready.
Unfortunately - we have had a long line of irresponsible parenting in society. I look at some parents and just think - they should not be having kids. I wish I had the ability to go and say look you are incapable and hence I revoke your reproduction rights, you are and will never be fit to have child. It reminds me a lot of the movie "Idiocracy". The dumb people are reproducing like bunnies while the smart people, want to be responsible, think, wait, make the right decision at the right time. The net result is a world full of crazy reproducing bunnies. Unfortunately, that just made me sound like a Nazi who wanted to revive th Nazi system of selective reproduction. It is socially and morally unpalatable that we tell which parents can reproduce or not.
So I guess we as a society will have to deal with bad parents and try to collectively fix the consequences and try to make it a better place. Or you can let me be a parenting Nazi and start a parenting department in the UN and dictate my tyranny on the worlds dumb parents and dumb teens.