Professor David Coleman from Dept of Social Policy, University of Oxford, gives a talk from his "Demographic Trends and Problems of the Modern World" series talking about the 'Second Demographic Transition'. The early 20th century was a time of very low divorce rates and of births outside marriage. Couples married late and many never married. In Western Europe, and the English-speaking world, all that changed after the 1960s; Cohabitation, divorce, births outside marriage made families much more diverse. The theory of the 'Second demographic transition' explains these trends as the result of new individual autonomy in a society now highly educated, secular and prosperous, with welfare arrangements supporting a variety of family types. As prosperity and education become globalised, the theory predicts that this diversity of behaviour will also be globalised. The lecture examines its scope and sustainability. Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/