Skip to main content

John Geanakoplos Publications

Publish Date
Abstract

We build a model of competitive pooling and show how insurance contracts emerge in equilibrium, designed by the invisible hand of perfect competition. When pools are exclusive, we obtain a unique separating equilibrium. When pools are not exclusive but seniority is recognized, we obtain a different unique equilibrium: the pivotal primary-secondary equilibrium. Here reliable and unreliable households take out a common primary insurance up to its maximum limit, and then unreliable households take out further secondary insurance.

Abstract

The possibility of default limits available liquidity. If the potential default draws nearer, a liquidity crisis may ensue, causing a crash in asset prices, even if the probability of default barely changes, and even if no defaults subsequently materialize.

Introducing default and limited collateral into general equilibrium theory (GE) allows for a theory of endogenous contracts, including endogenous margin requirements on loans. This in turn allows GE to explain liquidity and liquidity crises in equilibrium. A formal definition of liquidity is presented.

When new information raises the probability and shortens the horizon over which a fixed income asset may default, its drop in price may be much greater than its objective drop in value for two reasons: the drop in value reduces the relative wealth of its natural buyers and also endogenously raises the margin required for its purchase. The liquidity premium rises, and there may be spillovers in which other assets crash in price even though their probability of default did not change.

Keywords: Liquidity, default, collateral, crashes, general equilibrium, contracts, spillover, liquidity premium

JEL Classification: D4, D5, D8, D41, D52, D81, D82

Abstract

Our purpose in this paper is to unify international trade and finance in a single general equilibrium model. Our model is rich enough to include multiple commodities (including traded and nontraded goods), heterogeneous consumers in each country, multiple time periods, multiple credit markets, and multiple currencies. Yet our model is simple enough to be effectively computable. We explicitly calculate the financial and real effects of changes in tariffs, productivity, and preferences, as well as the effects of monetary and fiscal policy.

We maintain agent optimization, rational expectations, and market clearing (i.e., perfect competition with flexible prices) throughout. But because of the important role money plays, and because of the heterogeneity of markets and agents, we find that fiscal and monetary policy both have real effects. The effects of policy on real income, long-term interest rates, and exchange rates are qualitatively identical to those suggested in Mundell-Fleming (without the small country hypothesis), although our equilibrating mechanisms are different. However, because the Mundell-Fleming model ignores expectations and relative price changes, our model predicts different effects on the flow of capital, the balance of trade, and real exchange rates in some circumstances.

Abstract

This paper explores the general equilibrium impact of social security portfolio diversification into private securities, either through the trust fund or private accounts. The analysis depends critically on heterogeneities in saving, production, assets, and taxes. Limited diversification weakly increases interest rates, reduces the expected return on short-term investment (and the equity premium), decreases safe investment, increases risky investment and increases a suitably weighted social welfare function. However, the effects on aggregate investment, long-term capital values, and the utility of young savers hinges on assumptions about technology. Aggregate investment and long-term asset values can move in opposite directions.

Abstract

This paper explores the general equilibrium impact of social security portfolio diversification into private securities, either through the trust fund or private accounts. The analysis depends critically on heterogeneities in saving, production, assets, and taxes. Limited diversification weakly increases interest rates, reduces the expected return on short-term investment (and the equity premium), decreases safe investment, increases risky investment and increases a suitably weighted social welfare function. However, the effects on aggregate investment, long-term capital values, and the utility of young savers hinges on assumptions about technology. Aggregate investment and long-term asset values can move in opposite directions.

Research in Economics
Abstract

Our purpose in this paper is to unify international trade and finance in a single general equilibrium model. Our model is rich enough to include multiple commodities (including traded and nontraded goods), heterogeneous consumers in each country, multiple time periods, multiple credit markets, and multiple currencies. Yet our model is simple enough to be effectively computable. We explicitly calculate the financial and real effects of changes in tariffs, productivity, and preferences, as well as the effects of monetary and fiscal policy.

We maintain agent optimization, rational expectations, and market clearing (i.e., perfect competition with flexible prices) throughout. But because of the important role money plays, and because of the heterogeneity of markets and agents, we find that fiscal and monetary policy both have real effects. The effects of policy on real income, long-term interest rates, and exchange rates are qualitatively identical to those suggested in Mundell-Fleming (without the small country hypothesis), although our equilibrating mechanisms are different. However, because the Mundell-Fleming model ignores expectations and relative price changes, our model predicts different effects on the flow of capital, the balance of trade, and real exchange rates in some circumstances.

Keywords: Currency, cash, fiscal policy, montary policy, money, trade

JEL Classification: E5, E6, F1, F2, F3

Abstract

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment by thinking of assets as pools. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of adverse selection and signalling phenomena in a perfectly competitive, general equilibrium framework.

Perfect competition eliminates the need for lenders to compute how the size of their loan or the price they quote might affect default rates. It also makes for a simple equilibrium refinement, which we propose in order to rule out irrational pessimism about deliveries of untraded assets.

We show that refined equilibrium always exists in our model, and that default, in conjunction with refinement, opens the door to a theory of endogenous assets. The market chooses the promises, default penalties, and quantity constraints of actively traded assets.

Abstract

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of adverse selection, and signalling phenomena (including the Akerlof lemons model and Rothschild-Stiglitz insurance model) and some moral hazard problems in a general equilibrium framework.

Despite earlier claims about the nonexistence of equilibrium with adverse selection, we show that equilibrium always exists.

We show that more lenient punishment which encourages default may be Pareto improving because it allows for better risk spreading.

We define an equilibrium refinement that requires expected delivery rates for untraded assets to be reasonably optimistic. Default, in conjunction with this refinement, opens the door to a theory of endogenous assets. The market can choose default penalties and quantity constraints on sellers.

Abstract

In our previous paper we built a general equilibrium model of default and punishment in which equilibrium always exists and endogenously determines asset promises, penalties, and sales constraints. In this paper we interpret the endogenous sales constraints as equilibrium signals. By specializing the default penalties and imposing an exclusivity constraint on asset sales, we obtain a perfectly competitive version of the Rothschild-Stiglitz model of insurance. In our model their separating equilibrium always exists even when they say it doesn’t.

Abstract

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment by thinking of assets as pools. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of adverse selection and signalling phenomena (including the Rothschild-Stiglitz insurance model) in a general equilibrium framework.

In contrast to game-theoretic models of adverse selection, our perfectly competitive framework eliminates the need for lenders to compute how the size of their loan or the price they quote might affect default rates. The equilibrium refinement we propose, in order to rule out irrational pessimism about deliveries of untraded assets, is also simpler than its game-theoretic counterparts.

We show that refined equilibrium always exists in our model, and that default, in conjunction with refinement, opens the door to a theory of endogenous assets. The market chooses the promises, default penalties, and quantity constraints of actively traded assets.

Abstract

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of moral hazard, adverse selection, and signalling phenomena (including the Akerlof lemons model and Rothschild-Stiglitz insurance model) in a general equilibrium framework.

We impose a condition on the expected delivery rates for untraded assets that is similar to the trembling hand refinements used in game theory. Despite earlier claims about the nonexistence of equilibrium with adverse selection, we show that equilibrium always exists, even with exclusivity constraints on asset sales, and transactions-liquidity costs or information-evaluation costs for asset trade.

We show that more lenient punishment which encourages default may be Pareto improving because it allows for better risk spreading.

We also show that default opens the door to a theory of endogenous assets.

Abstract

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment by thinking of assets as pools. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of adverse selection and signalling phenomena in a perfectly competitive, general equilibrium framework.

Perfect competition eliminates the need for lenders to compute how the size of their loan or the price they quote might affect default rates. It also makes for a simple equilibrium refinement, which we propose in order to rule out irrational pessimism about deliveries of untraded assets.

We show that refined equilibrium always exists in our model, and that default, in conjunction with refinement, opens the door to a theory of endogenous assets. The market chooses the promises, default penalties, and quantity constraints of actively traded assets.

Abstract

We extend the standard model of general equilibrium with incomplete markets to allow for default and punishment. The equilibrating variables include expected delivery rates, along with the usual prices of assets and commodities. By reinterpreting the variables, our model encompasses a broad range of adverse selection and signalling phenomena (including the Akerlof lemons model and the Rothschild-Stiglitz insurance model) in a general equilibrium framework.

Despite earlier claims about the nonexistence of equilibrium with adverse selection, we show that equilibrium always exists.

We show that more lenient punishment which encourages default may be Pareto improving because it increases the dimension of the asset span without increasing the number of assets traded.

We define an equilibrium refinement that requires expected delivery rates for untraded assets to be reasonably optimistic. Default, in conjunction with this refinement, opens the door to a theory of endogenous assets. The market chooses the promises, default penalties, and quantity constraints of actively traded assets.

Abstract

This paper explores the general equilibrium impact of social security portfolio diversification into private securities, either through the trust fund or via private accounts. The analysis depends critically on heterogeneity in saving, in production, in assets, and in taxes. Under fairly general assumptions we show that limited diversification increases a neutral social welfare function, increases interest rates, reduces the expected return on short-term equity (and thus the equity premium), decreases safe investment and increases risky investment. However, the effect on aggregate investment, long-term capital values, and the utility of young savers hinges on delicate assumptions about technology. Aggregate investment and long-term asset values often move in the opposite direction. Thus social security diversification might reduce long-term equity value while it increases aggregate investment.