Fear of population decline has haunted states ever since states existed. Population size was the basis of the power, security and prosperity of any political entity. Slides to accompany Professor David Coleman's on the fear of population decline. The great disparity of economic and military power between the West and the Rest from the 18th century temporarily put population size into the shade. As that advantage ebbs, population size has emerged once again as a major factor in international relations, especially as population decline has become a reality in Germany, Japan and is forecast for many others. Many demographers believe that world population will begin to fall by the end of this century. However not all concerns about population decline are justified. Being small is certainly no obstacle to very high levels of living standards (Switzerland, Sweden, Iceland) or of reported happiness (Denmark). Some undesirable economic consequences follow the process of population decline but seem likely to be mild as long as long as decline is slow and eventually stops. Considerable environmental advantages would arise from smaller population - it may indeed become essential globally if climate change is not to force it upon us.