Population Size and the Quality of Life

Abstract

Types of Social Choice. In his recent book Derek Parfit distinguishes three types of policy options: Same People Choices, Same Number Choices and Different Numbers Choices; (Parfit (1984); see also Parfit (1982)). The first has no effect on the number of persons, nor indeed on their personal identities; as in the classic problem of dividing a cake fairly among a given group of people, or in analyses of the short run consequences of changes in immigration policies. Much social choice theory is concerned with this sort of issue. The second affects the identities of future persons but not their numbers. The last affects both. National economic plans are most often cast within the context of Same Number Choices. This is a good approximation when the available set of economic policies is restricted, either for technical or for political reasons, to those that do not impinge on the size of future populations. The idea then is to forecast future numbers (which, by assumption, are unaffected by choice of policy) and then to rank alternative policies. (See e.g. Graaff (1962), Chapter 6.) In Same People Choices, social states-or states of affairs-need not include in their characterisation the personal identities involved, since the same persons are affected by all the policies. By way of contrast, in Same Number Choices a social state includes in its characterisation the identities of the people involved, although, of course, the number of lives associated with all states of affairs is, by assumption, the same. To be sure, one may argue that personal