On why killing three billion people may not be such a bad idea

During a recent coffee conversation, members of the faculty were discussing on the difficulties of establishing Pareto optimality in situations with an infinite horizon. In cases like those, it is complex to ascertain what schedule of taxes and transfers from one generation to another can make all generations better off. At some point the conversation arrived at an extreme example: Suppose we kill half the population of the planet, that is, three billion people. That will ensure that global warming will not take place, that valuable resources will remain unexploited and that pollution will not ruin the environment forever. That is, the potential gains for future generations from an exercise like that are huge. The next step would be to compensate the three billion people we are about to kill in order to ensure a Pareto improvement. We could throw them a party wild and big enough to leave them indifferent between dying just after it ends or continue living. That is reminiscent of that old sci-fi film called Logan’s Run (in the photo) in which people in a dystopian society were “renewed” when they turned 30 in the middle of a ceremony with great celebration and joy. The incredible welfare gains derived from having half the population of the planet exterminated should be enough to compensate those who are killed and that would ensure Pareto optimality. There is however an obvious problem with this scheme: Those gains will take place in the future. Only after the three billion people are dead the rivers and the air will become clean, the level of the sea will stop threatening millions of people living in the coast and humans will avoid extinction. Unfortunately, those large welfare gains cannot be transferred from the future.

At this point you may be horrified. Morally, the idea of killing half of the Earth’s population seems repulsive at first glance. But what if it ensures the survival of the human race? Let’s put in a different way. Suppose now that people care about the welfare of their children and of their grandchildren. In that case, the transfer necessary to leave them indifferent between dying or not (the size of the party) may not be that big if by leaving things as they are their descendants will face extinction or, even worse, a miserable life. Maybe, just maybe, the total amount needed to compensate those three billion people is not that big and it can be generated by the current generation...

... This is what happens when you take economic reasoning to its last consequences.