Kottke has a post with this timeline map of the global median age from 1960 to 2060. It's interesting to see the various countries aging at different rates, until many of the OECD countries are median age of 50+.
But what's also striking is the correlation of young countries with unrest and war. For example, today the media age of Iraq, Afghanistan and a country in Central America (likely Guatemala) is in the teens. The other such countries are in central Africa.
So maybe the slogan of the 60's should have read: "make love and war", or "make love amidst war"?