23rd May 2018, 10.00 - 12.00, Institute for Futures Studies.
Sir Partha Dasgupta, Professor Emeritus of Economics at the University of Cambridge.
"Earth's Carrying Capacity and Optimum Global Population"
In this lecture I study fertility choice in the face of socio-ecological constraints. I assume that when choosing their family size, people exercise agent-centred prerogatives within an otherwise Classical Utilitarian outlook. People evaluate states of affairs on the basis of a weighted sum of personal well-beings, where the weight they award to potential well-beings of children they could have is less than the weight they award to their own well-being, knowing in advance that they will want to share resources with the children they produce on an equal basis. The gap between ex ante and ex post reasonings distinguishes the theory from Classical Utilitarianism; the latter admits no gap. The ecological constraint facing households is taken to be the biosphere, which is modelled as an open-access resource. I show that under that property-rights regime households are pro-natalist: there is population overshoot. I try the theory for size, using crude estimates of the biosphere's (human) carrying capacity. Using stylized figures for both positive and normative parameters in the model, I find that the globally optimum living standard is higher than the current 15,000 international dollars, and that the globally optimum population size is considerably smaller than the current 7.5 billion. The numerical estimates are contrasted from estimates drawn from Classical Utilitarianism.