Population size: Individual choice and social optima

Optimal population size when fertility is endogenous is considered in relation to two social welfare criteria, a Benthamite and a Millian, and in relation to purely individualistic maximization of utility in the current generation. We show that a tax-subsidy scheme involving child allowances and subsidies to future generation consumption can be found to support a social optimum through individual choice. A general proof that the optimal population size according to the Benthamite criterion is always larger than that given by the Millian criterion is presented, but we show that no general conclusions about the size of the population under laissez-faire are possible.