Observer: The science of demographic projection and the art of scaremongering enjoy a relationship akin to that of the sadist and masochist: first comes the threat, then the relish with which the punishment is anticipated. Thus forecasts of increasing population numbers are guaranteed to produce dystopian visions of social collapse. The godfather of apocalyptic demographics was the Rev Thomas Malthus, who famously proposed in the late 18th century that unchecked population growth would lead to …