Overlapping Generations: the First Jubilee.

Paul Samuelson's (1958) overlapping generations model has turned 50. Seldom has so simple a model been so influential. The paper, in spite of its ripe age, still elicits wonder. Starting from the uncontroversial observation that “we live in a world where new generations are always coming along” Samuelson built a model that violates the credo of the first fundamental welfare theorem with which we still inculcate undergraduates 50 years later. According to Samuelson, all is not necessarily well in the best of market economies: with overlapping generations, even absent the usual suspects such as distortions and market failures, a competitive equilibrium need not be Pareto efficient. Worst of all, this failure of the first welfare theorem in an overlapping generations model occurs in a framework that is, in many ways, more plausible and realistic than the world of agents living synchronous and finite existences in which the theorem is usually proved. Like Mona Lisa's enigmatic smile, the mysterious welfare properties of the overlapping generations model are, to a significant extent, responsible for its popularity—along with the many economic issues it has illuminated in the last half-century. I take it as my brief in this celebratory paper to provide, after a short exposition of the main results of the overlapping generations model under certainty, an explanation of why the welfare properties of the overlapping generations model differ so much from the canonical Arrow–Debreu framework and to review, in a deliberately nonencyclopedic mode, a few striking applications and extensions of Samuelson's deceptively straightforward model.

Reflections on the Fiscal Theory of the Price Level.

In a world in which consumers correctly expect that both Ricardian and non-Ricardian policy regimes are possible in the future, the fiscal theory of the price level is valid, yet the price is indeterminate. This result does not rely on imposing that the initial stock of nominal bonds be strictly positive, and it does not require a surprise ex post revaluation of nominal assets.

Macroeconomics of Credit and Labor Markets Imperfections.

Credit market imperfections influence the labor market and aggregate economic activity. In turn, macroeconomic factors have an impact on the credit sector. To assess these effects in a tractable general-equilibrium framework, we introduce endogenous search frictions, in the spirit of Peter Diamond (1990), in both credit and labor markets. We demonstrate that credit frictions amplify macroeconomic volatility through a financial accelerator. The magnitude of this general-equilibrium accelerator is proportional to the credit gap, defined as the deviation of actual output from its perfect credit market level. We explore various extensions, notably endogenous wages.

Risk Aversion and Intertemporal Substitution in the Capital Asset Pricing Model

When tastes are represented by a class of generalized preferences which -- unlike traditional Von-Neumann preferences -- do not confuse behavior towards risk with attitudes towards intertemporal substitution, the true beta of an asset is, in general, an average of its consumption and market betas. We show that the two parameters measuring risk aversion and intertemporal substitution affect consumption and portfolio allocation decisions in symmetrical ways. A unit elasticity of intertemporal substitution gives rise to myopia in consumption-savings decisions (the future does not affect the optimal consumption plan), while a unit coefficient of relative risk aversion gives rise to myopia in portfolio allocation (the future does not affect optimal portfolio allocation). The empirical evidence is consistent with the behavior of intertemporal maximizers who have a unit coefficient of relative risk aversion and an elasticity of intertemporal substitution different from 1.

Menus of Linear Income Tax Schedules

Relative to traditional piecewise linear income taxation schemes, it is possible to increase government revenues by offering to consumers a menu of linear income tax schedules. In the resulting Pareto-superior equilibrium, consumers sort themselves out according to their (unobservable) productivity level, with high productivity agents choosing the tax schedules with low marginal tax rate and high intercept. This scheme extracts from the economy an unexploited source of revenue which, in contrast with standard supply-side proposals, does not depend on the economy being on the downward-sloping side of the Laffer curve.

Approximate Equilibrium Asset Prices.

Arguing that total consumer wealth is unobservable, we invert the (approximate) consumption function to reconstruct, in a world with Kreps-Porteus generalized isoelastic preferences, i) the wealth that supports the agents’ observed consumption as an optimal outcome and ii) the rate of return on the consumers’ wealth portfolio. This allows us to (approximately) price assets solely as a function of their payoffs and of consumption — in both homoskedastic or heteroskedastic environments. We compare implied equilibrium returns on the wealth portfolio to observed stock market returns and gauge whether the stock market is a good proxy for unobserved aggregate wealth.Asset pricing, Kreps-Porteus, Epstein-Zin-Weil preferences;