Knowledge that Transforms

This paper analyzes a decentralized process for the diffusion of knowledge. In equilibrium, the economy converges from an initial distribution of knowledge over agents to the steady-state distribution, which is unique. Because of the public good aspect of information, too little learning takes place, and ideas are implemented too early. The key difference between earlier formulations of search externalities by Diamond, Mortensen, and Spence on the one hand, and our own on the other, is that here spillovers of knowledge depend not only on how hard people are trying, but also on the differences in what they know: if all of us know the same thing, we cannot learn from each other. The model also addresses the following two substantive questions: first, the relationship between inequality and growth, noted some time ago by Kuznets, and second, the effect on growth of improvements in the communication technology.

Agents expect to trade with each other infinitely often, but face a temporal absence of a coincidence of wants when they meet. Only loans and/or money can facilitate exchange. In small close-knit economies, enduring trade relationships are valued and loans are optimal. In larger economies, with limited communication, information concerning repayment of loans diffuses too slowly to deter agents from reneging unless loans are severely restricted in magnitude. Money has no such redeemability problems, but if Clower constraints bind, loans help supplement money purchases so that both become essential. Roles of various institutions and the historical evolution of media of exchange are explained.

This paper presents simple conditions and a simple proof of the existence of equilibrium in asset markets where short-selling is allowed and satiation is possible. Unlike standard nonsatiation assumptions, the one used here is weak enough to be reasonable in the mean-variance capital asset pricing model and in asset market models where investors maximize expected utility and where total returns to individual assets may be negative. Copyright 1989 by The Review of Economic Studies Limited.

The authors estimate a model of production and investment based on the theory of dynamic duality. They are particularly interested in the effects of R&D spillovers and in calculating the social and private rates of return. Cost-reducing, factor-biasing and capital-adjustment spillover effects are estimated for four industries. The existence of R&D spillovers implies that the social and private rates of return to R&D capital differ. The authors estimate that the social return exceeds the private return in each industry. Moreover, there is significant variation across industries in the differential between the social and private rates of return. Copyright 1989 by The Review of Economic Studies Limited.

The purpose of this paper is to explore the welfare properties of dynastic equilibria. There are three central findings. First, under relatively weak conditions, welfare optima cannot be implemented as dynastic equilibria with positive levels of transfers. Second, intergenerational altruism ordinarily renders the objectives of social planners dynamically inconsistent, thereby making implementation of welfare optima problematic. Third, if a planner successfully resolves dynamic inconsistency by committing himself to respect the preferences of deceased generations, then, in a specific set of cases, dynastic equilibria are approximately welfare optimal. Copyright 1989 by The Review of Economic Studies Limited.

This paper studies the welfare properties of the equilibrium timing of price changes. Staggered price setting has the advantage that it permits rapid adjustment to firm-specific shocks, but the disadvantages that it causes unwanted fluctuations in relative prices and that, by creating price level inertia, it can increase aggregate fluctuations. Because each firm ignores its contribution to these problems, staggering can be a stable equilibrium even if it is highly inefficient. In addition, there can be multiple equilibria in the timing of prices changes; indeed, whenever there is an inefficient staggered equilibrium, there is also an efficient equilibrium with synchronized price setting.

We propose a specific characteristics framework in order to construct linkages between alternative conceptual approaches to modelling product differentiation. First, it is shown that a demand system which satisfies the gross substitutes property imposes specific requirements on the locations of products. In particular, the dimension of the characteristics space must be larger than or equal to the number of products minus one. We then identify a method for casting a given demand system (subject to certain restrictions) into our characteristics framework. This is illustrated for the logit, probit and linear probability models of discrete choice theory. Finally, we find a characteristics representation of the CES representative consumer.

This paper considers a small open economy with a safe sector and a risky sector. The probability of success in the risky activity differs across individuals, and is private information. It is shown that policies that sustain informationally constrained Pareto optima should not include tariffs. A laissez-faire competitive equilibrium, if it exists, is Pareto optimal. These results contrast with previous literature on the role of tariffs as insurance, where private risk markets are assumed away in an ad hoc manner.

This paper considers a stochastic, time-varying interest rate in a continuous-time, inventory-theoretic model of the demand for money. The problem of minimizing expected, discounted cash-management costs is ascribed to an agent. An optimal cash-management policy exists and is of a familiar target-threshold form. Closed-form expressions for the forward-looking, time-varying targets and thresholds are derived in special cases and implications for the dynamics of the cash balance are described. Copyright 1989 by The Review of Economic Studies Limited.

The issue of dynamic efficiency is central to analyses of capital accumulation and economic growth. Yet the question of what characteristics should be examined to determine whether actual economies are dynamically efficient is unresolved. This paper develops a criterion for determining whether an economy is dynamically efficient. The criterion, which holds for economies in which technological progress and population growth are stochastic, involves a comparison of the cash flows generated by capital with the level of investment. Its application to the United States economy and the economies of other major OECD nations suggests that they are dynamically efficient.