The Supply of Social Insurance

We propose a theory of the welfare state, in which social transfers are chosen by a governing group interacting with non-governing groups repeatedly. Social demands from the non-governing groups are credible because these groups have the ability to generate social conflict. In this context social insurance is supplied as an equilibrium response to income risks within a self-enforcing social contract. When we explore the implications of such a view of the social contract, we find four main determinants of the welfare state: the degree of aggregate income risk; the heterogeneity of group-specific income risks; the public administration’s ability to implement group-specific transfers; and the ability of the non-governing groups to coordinate their social demands. We also analyze the link between public good provision and social insurance

An Equilibrium Theory of Declining Reservation Wages and Learning

In this paper we consider learning from search as a mechanism to understand the relationship between unemployment duration and search outcomes as a labor market equilibrium. We rely on the assumption that workers do not have precise knowledge of their job finding probabilities and therefore, learn about them from their search histories. Embedding this assumption in a model of the labor market with directed search, we provide an equilibrium theory of declining reservation wages over unemployment spells. After each period of search, unemployed workers update their beliefs about the market matching efficiency. We characterize situations where reservation wages decline with unemployment duration. Consequently, the wage distribution is non-degenerate, despite the facts that matches are homogeneous and search is directed. Moreover, aggregate matching probability decreases with unemployment duration, in contrast to individual workers' matching probability, which increases over individual unemployment spells. The difficulty in establishing these results is that learning generates non-differentiable value functions and multiple solutions to a worker's optimization problem. We overcome this difficulty by exploiting a connection between convexity of a worker's value function and the property of supermodularity.Reservation wages; Learning; Directed search; Supermodularity

An Equilibrium Theory of Learning, Search and Wages

We construct an equilibrium theory of learning from search in the labor market, which addresses the search behavior of workers, the creation of jobs, and the wage distribution as functions of unemployment duration. In the model, each worker has incomplete information about his job-finding ability and learns about it from his search outcomes. The theory formalizes a notion akin to that of discouragement: over the unemployment spell, unemployed workers update their beliefs about their job-finding abilities downward and reduce their desired wages. One contribution of the paper is to integrate learning from search into an equilibrium framework. We show that the equilibrium exhibits wage dispersion among homogeneous workers, and that workers with longer unemployment spells have lower permanent incomes. Another contribution is to apply lattice-theoretic techniques to analyze learning from experience, which is useful because learning generates convex value functions and, in principle, multiple solutions to a worker's optimization problem.Learning; Wages; Unemployment; Directed search; Supermodularity.

Deformations of canonical triple covers

In this paper, we show that if X is a smooth variety of general type of dimension m≥3 for which the canonical map induces a triple cover onto Y, where Y is a projective bundle over P1 or onto a projective space or onto a quadric hypersurface, embedded by a complete linear series (except Q3 embedded in P4), then the general deformation of the canonical morphism of X is again canonical and induces a triple cover. The extremal case when Y is embedded as a variety of minimal degree is of interest, due to its appearance in numerous situations. For instance, by looking at threefolds Y of minimal degree we find components of the moduli of threefolds X of general type with KX3=3pg−9,KX3≠6, whose general members correspond to canonical triple covers. Our results are especially interesting as well because they have no lower dimensional analogues

Deformations of canonical double covers

In this paper we show that if X is a smooth variety of general type of dimension m≥2 for which its canonical map induces a double cover onto Y, where Y is the projective space, a smooth quadric hypersurface or a smooth projective bundle over P1, embedded by a complete linear series, then the general deformation of the canonical morphism of X is again canonical and induces a double cover. The second part of the article proves the non-existence of canonical double structures on the rational varieties above mentioned. Our results have consequences for the moduli of varieties of general type of arbitrary dimension, since they show that infinitely many moduli spaces of higher dimensional varieties of general type have an entire “hyperelliptic” component. This is in sharp contrast with the case of curves or surfaces of lower Kodaira dimension