A few scatterbrained musings on demography and social stability:
China's "one child" policy (which has exemptions for about two-thirds of their populace) has had the unforeseen consequence of a gender imbalance as unwanted female children are aborted. It seems that by 2020 we may expect 30 million single Chinese men of marriageable age. The link just given also cites statistics that suggest this imbalance is generally associated with more crime, aggressive expansionism etc (BBC News estimates 24 million). Niall Ferguson worried about the implications last year.
I wondered whether homosexuality (which has an ancient history in China) might take off some of the stress; it's been legal again there since 1997. But an official Chinese statistic from 2005 is that only 2.3% of the population are gay (some 30 million people, says a Wiki entry on their LGBT) - about the same proportion as in the UK, unless you believe Stonewall's attempts to inflate the figure.
A linked issue is age imbalance: it's been theorised that a "youth bulge" is a factor in civil unrest. The Chinese attempt to control the birthrate as more of their people survive and age, may have saved us from war triggered by the need for lebensraum. But other countries (especially in the Middle East and North Africa, where a Puritan Islamic revival is in progress) are experiencing this bulge and the young singles are strongly discouraged from seeking a sexual outlet for their energies.
Would it help if they got their end away more? Is it Eros v. Thanatos? But from what I read, young criminals in the UK don't seem to me to be sublimating their sex drives into their professional activities.
Having said that, women in wealthier countries show a tendency to delay having their first child (age 29 in the UK) and in countries ravaged by war (e.g. Angola) the picture is not clear but suggests that when some sort of stability returns women may "catch up" foregone childbirth but may then become reluctant to continue bearing more children (see page 13 of this study on Angola). In the latter case, we may see a sort of temporary "baby boom" which, combined with the loss of older individuals in war, could itself create another "youth bulge".
This entry includes a graph showing a correlation between GDP per capita and number of children born per woman; outliers are Angola (already mentioned), Saudi Arabia, Israel and the USA. I wonder whether these discrepancies are influenced not just by religion but economic inequality within those nations, particularly in Saudi and America? This paper suggests that poorer people invest less in education and more in having larger families, so maybe there should be better public education for all.
I'd like to see more for young people to do in the UK. The youths where I live amuse themselves by throwing stones at light fittings outside the am-dram theatre, and setting fire to plastic litter bins. Since I came here 30 years ago, most of the shops have installed steel shutters, a sure sign that an area is going to the bow-wows. Paid work would sort a lot of this, I think. And it may seem sexist, but I think work is especially important for men - women seem more capable of occupying themselves relatively productively and peacefully. Or have I got that wrong?