1 Sustainable Welfare and Optimum Population Size Theodore P. Lianos 1 & Anastasia Pseiridis 2 Published in Environment, Development and Sustainability (Springer), 19 Sept 2015. The final publication is available at Springer via http://dx.doi.org/10.1007/s10668-015- 9711-5 1 Professor Emeritus of Political Economy, Department of Economics, Athens University of Economics and Business tplianos@aueb.gr 2 Assistant Professor, Department of Economics and Regional Development, Panteion University and Tutor, Hellenic Open University, School of Social Sciences pseiridis@panteion.gr Abstract This paper is an attempt to estimate the level of sustainable welfare, namely a level of consumption that can be enjoyed by all future generations. Based on available measures of the ecological footprint and biocapacity, and assuming an acceptable level of per capita consumption, we estimate the maximum level of world population which will allow a level of consumption without damaging the natural productive capacity of the earth. Also, based on a criterion of the ability of each country to feed its people, we estimate the maximum size of population for the fifty most populated countries. It turns out that a few countries are underpopulated (Argentina, Canada, Russia, etc), but most are overpopulated (China, India, Japan, etc). We conclude by emphasizing the need for an ecumenical effort to educate and inform people about the need to reduce world population. Keywords: population, sustainable welfare, ecological footprint, biocapacity. Acknowledgments The authors are grateful to unknown reviewers for valuable comments and suggestions, to colleagues for useful discussions, and to Ms Genevieve Gorgos for discussion and linguistic improvements. Also, thanks are due to the Earth Policy Institute and the Global Footprint Network for providing the data used in this study.