"Optimum population" is a subject long discussed in welfare economics. The talk will first discuss the framework for analysis of policy. This leads to a discussion of the implications of population growth for justice at a global level and the evolution of global inequality. The final part of the talk is concerned with population growth and the setting of global goals post-2015. Professor Sir Tony Atkinson, Deputy Director, Institute for New Economic Thinking @ Oxford; Professor of Economics, Oxford University.