Spengler at Asian Times suggests that Iran is already collapsing economically, and by 2030 they will have very few young people in which to drive the workforce and military. Interesting stuff. But demographics is not necessarily a hallmark of social collapse. The US after all has a more skewed demographic distribution due to the baby boomers. We are hardly a society in the state of collapse. But his basic point is that a culture which fails to replace its population or expand the population by definition will cease to exist. Hard to believe that a culture or a society will actually choose to 'go extinct' if you would. Yet that is the suggestion. I'm sceptical, but it's an interesting point of view.