Forthcoming: K. Bykvist and T. Campbell, eds., Oxford Handbook of Population Ethics (Oxford: Oxford University Press) Population Overshoot by Aisha Dasgupta* and Partha Dasgupta** 20 September 2018 Final Revision: 15 January 2019 * United Nations Population Division e-mail: <
[email protected]> ** Faculty of Economics, University of Cambridge; and New College of the Humanities, London e-mail: <
[email protected]> The views expressed in this paper are entirely those of the authors and do not necessarily reflect the views of the United Nations. For their most helpful comments on a previous draft we are grateful to Krister Bykvist, Timothy Campbell, John Cleland, Rachel Friedman, and Robert Solow. 1 Contents Motivation Part I The Desire for Children 1 Rich and Poor: Consumption and Population 2 Two Classes of Externalities 3 Reproductive Rights 4 Socially Embedded Preferences and Conformism 5 Unmet Need, Desired Family Size, and the UN's Sustainable Development Goals Part II How Many People Can Earth Support in Comfort? 6 Ecosystem Services 7 The Biosphere as a Capital Asset 8 Technology and Institutions References Figure 1 Table 1 Figure 2 Figure 3 2 Motivation Ehrlich and Holdren (1971) introduced the metaphor, I=PAT, to draw attention to the significance of the biosphere's carrying capacity for population ethics. The authors traced the impact of human activities on the Earth system to population, affluence (read, per capita consumption of goods and services), and the character of technology in use (including institutions and social capital). Because our impact on the biosphere is proportional to the demands we make of it, and because those demands increase with our economic activity, we can assume our impact on the biosphere increases with economic activity.