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Factor saving innovation
We study a simple model of factor saving technological innovation in a concave framework. Capital can be used either to reproduce itself or, at additional cost, to produce a higher quality of capital that requires less labor input. If higher quality capital can be produced quickly, we get a model of exogenous balanced growth as a special case. If, however, higher quality capital can be produced slowly, we get a model of endogenous growth in which the growth rate of the economy and the rate of adoption of new technologies are determined by preferences, technology, and initial conditions. ...
Journal Article
Failing to Provide Public Goods: Why the Afghan Army Did Not Fight
The theory of public goods is mainly about the difficulty in paying for them. Our question here is this: Why might public goods not be provided, even if funding is available? We use the Afghan Army as our case study. We explore this issue using a simple model of a public good that can be provided through collective action and peer pressure, by modeling the self-organization of a group (the Afghan Army) as a mechanism design problem. We consider two kinds of transfer subsidies from an external entity such as the U.S. government. One is a Pigouvian subsidy that simply pays the salaries, ...
Working Paper
Evolving to the impatience trap: the example of the farmer-sheriff game
The literature on the evolution of impatience, focusing on one-person decision problems, finds that evolutionary forces favor the more patient individuals. This paper shows that in the context of a game, this is not necessarily the case. In particular, it offers a two- population example where evolutionary forces favor impatience in one group while favoring patience in the other. Moreover, not only evolution but also efficiency may prefer impatient individuals. In our example, it is efficient for one population to evolve impatience and for the other to develop patience. Yet, evolutionary ...
Working Paper
An approximate dual-self model and paradoxes of choice under risk
We derive a simplified version of the model of Fudenberg and Levine [2006, 2011] and show how this approximate model is useful in explaining choice under risk. We show that in the simple case of three outcomes, the model can generate indifference curves that ?fan out? in the Marshack-Machina triangle, and thus can explain the well-known Allais and common ratio paradoxes that models such as prospect theory and regret theory are designed to capture. At the same time, our model is consistent with modern macroeconomic theory and evidence and generates predictions across a much wider set of ...
Conference Paper
Technological diversification - discussion
Report
Bankruptcy and collateral in debt constrained markets
Typical models of bankruptcy and collateral rely on incomplete asset markets. In fact, bankruptcy and collateral add contingencies to asset markets. In some models, these contingencies can be used by consumers to achieve the same equilibrium allocations as in models with complete markets. In particular, the equilibrium allocation in the debt constrained model of Kehoe and Levine (2001) can be implemented in a model with bankruptcy and collateral. The equilibrium allocation is constrained efficient. Bankruptcy occurs when consumers receive low income shocks. The implementation of the debt ...
Working Paper
Debt constrained asset markets
We develop a theory of general equilibrium with endogenous debt limits in the form of individual rationality constraints similar to those in the dynamic consistency literature. If an agent defaults on a contract, he can be excluded from future contingent claims markets trading and can have his assets seized. He cannot be excluded from spot markets trading, however, and he has some private endowments that cannot be seized. All information is publicly held and common knowledge, and there is a complete set of contingent claims markets. Since there is complete information, an agent cannot enter ...
Working Paper
On characterizing equilibria of economies with externalities and taxes as solutions to optimization problems
We characterize equilibria of general equilibrium models with externalities and taxes as solutions to optimization problems. This characterization is similar to Negishi?s characterization of equilibria of economies without externalities or taxes as solutions to social planning problems. It is often useful for computing equilibria or deriving their properties. Frequently, however, finding the optimization problem that a particular equilibrium solves is difficult. This is especially true in economies with multiple equilibria. In a dynamic economy with externalities or taxes there may be a ...
Report
Perfectly competitive innovation
We construct a competitive model of innovation and growth under constant returns to scale. Previous models of growth under constant returns cannot model technological innovation. Current models of endogenous innovation rely on the interplay between increasing returns and monopolistic markets. In fact, established wisdom claims monopoly power to be instrumental for innovation and sees the nonrivalrous nature of ideas as a natural conduit to increasing returns. The results here challenge the positive description of previous models and the normative conclusion that monopoly through copyright and ...
Working Paper
The optimum quantity of money revisited
This paper uses a simple general equilibrium model in which agents use money holdings to self insure to address the classic question: What is the optimal rate of change of the money supply? The standard answer to this question, provided by Friedman, Bewley, Townsend, and others, is that this rate is negative. Because any revenues from seignorage in our model are redistributed in lump-sum form to agents and this redistribution improves insurance possibilities, we find that the optimal rate is sometimes positive. We also discuss the measurement of welfare gains or losses from inflation and ...