Skip to main content

Martin Shubik Publications

Publish Date
Abstract

The knowledge constraints and transactions costs imposed by geographical distance, network connections and time conspire to justify local behavior as a good approximation for global rationality. We consider a class of games to illustrate this relationship and raise some questions as to what constitutes a satisfactory solution concept.

Abstract

Although short sales make an important contribution to financial markets, this transaction faces legal constraints that do not govern long positions. In evaluating these constraints, other commentators, who are virtually all economists, have not focused rigorously enough on the precise contours of current law. Some short sale constraints are mischaracterized, while others are omitted entirely. Likewise, the existing literature neglects many strategies in which well advised investors circumvent these constraints; this avoidance may reduce the impact of short sale constraints on market prices, but may contribute to social waste in other ways. To fill these gaps in the literature, this paper offers a careful look at current law and draws three conclusions. First, short sales play a valuable role in the financial markets; while there may be plausible reasons to regulate short sales — most notably, concerns about market manipulation and panics — current law is very poorly tailored to these goals. Second, investor self-help can ease some of the harm from this poor tailoring, but at a cost. Third, relatively straightforward reforms can eliminate the need for self-help while accommodating legitimate regulatory goals. In making these points, we focus primarily on a burden that other commentators have neglected: profits from short sales generally are ineligible for the reduced tax rate on long-term capital gains, even if the short sale is in place for more than one year.

Abstract

The relationship between money and credit is discussed in terms of network linkage. Fiat money is the only instrument with the universal recognition of its issuer. Near monies such as bank money and money substitutes such as gasoline credit cards can be classified in terms of their network links. This leads to a way of considering the velocity of money.

Abstract

The relationship between money and credit is discussed in terms of network linkage. Fiat money is the only instrument with the universal recognition of its issuer. Near monies such as bank money and money substitutes such as gasoline credit cards can be classified in terms of their network links. This leads to a way of considering the velocity of money.

Keywords: Credit, fiat money, networks, trust, velocity

JEL Classification: E5, E4, C7

Abstract

We construct explicit equilibria for strategic market games used to model an economy with fiat money, one nondurable commodity, countably many time- periods, and a continuum of agents. The total production of the commodity is a random variable that fluctuates from period to period. In each period, the agents receive equal endowments of the commodity, and sell them for cash in a market; their spending determines, endogenously, the price of the commodity. All agents have a common utility function, and seek to maximize their expected total discounted utility from consumption.

Suppose an outside bank sets an interest rate rho for loans and deposits. If 1+rho is the reciprocal of the discount factor, and if agents must bid for consumption in each period before knowing their income, then there is no inflation. However, there is an inflationary trend if agents know their income before bidding.

We also consider a model with an active central bank, which is both accurately informed and flexible in its ability to change interest rates. This, however, may not be sufficient to control inflation.

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

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.