 A third development worth mentioning has to do with population ethics. Sum-utilitarianism appears to be overly populationist, since it implies the “repugnant conclusion” (Parfit 1984) that we should aim for an unhappy but sufficiently large population in preference to a small and happy one. Conversely, average utilitarianism is “Malthusian”, preferring a happier population, no matter how small, to a less happy one, no matter how large. Here again there is an interesting tension, namely, between accepting all individuals whose utility is greater than zero, accepting equalization of utilities, and avoiding the “repugnant conclusion”. This tension is shown in this way. Start with a given affluent population of any size. Add any number of individuals with positive but almost zero utilities. This does not reduce social welfare. Then equalize utilities, which again does not reduce social welfare. One then obtains, compared to the initial population, a larger population with lower utilities. One sees that these lower utilities may be arbitrarily low, if the added individuals are sufficiently numerous and have sufficiently low initial utilities, thus yielding the repugnant conclusion (see Arrhenius 2000). Average utilitarianism disvalues additional individuals whose utility is below the average, which is very restrictive for affluent populations. A less restrictive approach is that of critical-level utilitarianism, which disvalues only individuals whose utility level is below some fixed, low but positive threshold. For an extensive overview and a defense of critical-level utilitarianism, see Blackorby, Bossert and Donaldson (1997, 2005), as well as Broome (2004). For an original proposal relying on a different social welfare function (inspired by the Gini function), see Asheim and Zuber (2014).