Whether or not to vaccinate one’s child is a decision that a parent may approach in several ways. The vaccination game, in which parents must choose whether to vaccinate a child against a disease, is one with positive externalities (herd immunity). In some societies, not vaccinating is an increasingly prevalent behavior, due to deleterious side effects that parents believe may accompany vaccination.
The standard game-theoretic approach assumes that parents make decisions according to the Nash behavioral protocol, which is individualistic and non-cooperative. Because of the positive externality that each child’s vaccination generates for others, the Nash equilibrium suffers from a free-rider problem. However, in more solidaristic societies, parents may behave cooperatively –they may optimize according to the Kantian protocol, in which the equilibrium is efficient. We test, on a sample of six countries, whether childhood vaccination behavior conforms better to the individualistic or cooperative protocol. In order to do so, we conduct surveys of parents in these countries, to ascertain the distribution of beliefs concerning the subjective probability and severity of deleterious side effects of vaccination.
We show that in all the countries of our sample the Kant model dominates the Nash model. We conjecture that, due to the free-rider problem inherent in the Nash equilibrium, a social norm has evolved, quite generally, inducing parents to vaccinate with higher probability than they would in the non-cooperative solution. Kantian equilibrium offers one precise version of such a social norm.
We calibrate a sequence of four nested models to study the dynamics of wealth accumulation. Individuals maximize a utility function whose arguments are consumption and investment. They desire to accumulate wealth for its own sake — this is not a life-cycle model. A competitive firm produces a single good from labor and capital; the rate of return to capital and the wage rate are market-clearing. The second model introduces political lobbying by the wealthy, whose purpose is to reduce the tax rate on capital income. The third model introduces differential rates of return to capitals of different sizes. The fourth model introduces inheritance and intergenerational mobility.
We study a vertically differentiated market where two firms simultaneously choose the quality and price of the good they sell and where consumers also care for the average quality of the goods supplied. Firms are composed of two factions whose objectives differ: one is maximizing profit while the other maximizes revenues. The equilibrium concept we model, called Firm Unanimity Nash Equilibrium (FUNE), corresponds to Nash equilibria between firms when there is efficient bargaining between the two factions inside both firms. One conceptual advantage of FUNE is that oligopolistic equilibria exist in pure strategies, even though the strategy space (price, quality) is multi-dimensional.
We first show that such equilibria are inefficient, with both firms underproviding quality. We then assume that the government takes a participation in one firm, which introduces a third faction, bent on welfare maximization, in that firm. We study the characteristics of equilibria as a function of the extent of government’s participation. Our main results are twofold. First, government’s participation in the firm providing the low quality good decreases efficiency while participation in the firm providing the high quality good increases efficiency. Second, the optimal degree of government’s participation in the high-quality firm increases with how much consumers care for average equality.