Knowledge that Transforms

This paper specifies and empirically analyzes a continuous-time, linear-quadratic, representative consumer model wit h time-nonseparable preferences of several forms. Within this framewor k, the author shows how time aggregation and time nonseparabilities in preferences over consumption streams can interact. The behavior of b oth seasonally adjusted and unadjusted consumption data is consistent wi th time-nonseparable preferences if consumption goods are durable and i f individuals develop habit over the flow of services from the good. T he data do not support a version of the model that ignores time nonseparabilities in preferences and focuses solely upon time aggregation. Copyright 1993 by The Econometric Society.

A system of consumer expenditure functions is estimated from Norwegian household budget data. Specific features o f our approach are: (I) Panel data on individual households are used, which offer far richer opportunities for identification, estimation and testing than usual cross section data. (II) Measurement errors are carefully modelled. Total consumption expenditure is modelled as a latent variable, purchase expenditures on different goods and two income measures are used as indicators of this basic latent variable. (III) The distribution of latent total expenditure across households, and its evolution over time, is estimated and important properties tested. (IV) Individual differences in preferences, represented by individual, time invariant latent variables, are modelled, identified, estimated, and tested. (V) We test the hypothesis that preferences are uncorrelated with total consumption expenditure, which is basic to all cross section estimation of consumer demand functions. (VI) The model can be formalized as a special case of the LISREL model, and the maximum likelihood algorithm of the computer program LISREL VI is applied.

Each of n players, in an infinitely repeated game, starts with subjective beliefs about his opponents' strategies. If the individual beliefs are compatible with the true strategies chose, then Bayesian updating will lead in the long run to accurate prediction of the future of play of the game. It follows that individual players, who know their own payoff matrices and choose strategies to maximize their expected utility, must eventually play according to a Nash equilibrium of the repeated game. An immediate corollary is that, when playing a Harsanyi-Nash equilibrium of a repeated game of incomplete information about opponents' payoff matrices, players will eventually play a Nash equilibrium of the real game, as if they had complete information.

This paper introduces the concept of standard risk aversion. A von Neumann-Morgenstern utility function has standard risk aversion if any risk makes a small reduction in wealth more painful (in the sense of an increased reduction in expected utility) also makes any undesirable, independent risk more painful. It is shown that, given monotonicity and concavity, the combination of decreasing absolute risk aversion and decreasing absolute prudence is necessary and sufficient for standard risk aversion. Standard risk aversion is shown to imply not only Pratt and Zeckhauser's 'proper risk aversion" (individually undesirable, independent risks always being jointly undesirable) , but also that being forced to face an undesirable risk reduces the optimal investment in a risky security with and independent return. Similar results are established for the effect of broad class of increases in one risk on the desirability of (or optimal investment in) a second, independent risk.

Perfect equilibria of finitely repeated games may be vulnerable to the possibility of renegotiation among players. We study the limiting properties of the set of payoffs from equilibria that are immune to renegotiation. Our main result is that the limit of the set of payoffs from renegotiation proof equilibria is either a singleton or a connected subset of the Pareto efficient frontier. A simple sufficient condition for the latter to occur is also provided.

The debate between the North and the South about the enforcement of intellectual property rights is examined within a dynamic general equilibrium framework in which the North invents new products and the South imitates them. A welfare evaluation of a policy of tighter intellectual property rights is provided by decomposing its response into four items: (1) terms of trade; (2) production composition; (3) available products; and (4) intertemporal allocation of consumption The paper proceeds in stages. It begins with an exogenous rate of innovation in order to focus on the first two elements. The following two components are added by endogenizing the rate of innovation. Finally, foreign direct investment is added to the model. Copyright 1993 by The Econometric Society.

A model of optimal consumption and portfolio choice that captures the notions of local substitution and irreversible purchases of durable goods is studied. Necessary and sufficient conditions for a consumption and portfolio policy to be optimal are provided. A closed-form solution of the optimal consumption and portfolio policy is given. The optimal consumption policy consists of a possible initial "gulp" of consumption, or a period of no consumption, followed.by a process of accumulated consumption with singular sample paths. The equilibrium risk premium in a representative investor economy with a single physical production technology is computed. Copyright 1993 by The Econometric Society.

June 1988, revised April 1992

A common finding in many of the recent empirical studies with the ARCH class of models applied to high frequency financial data concerns the apparent persistence of shocks for forecast of the future conditional variances. It is likely that several different variables share this same implied long-run component, however. In that situation, the variables are defined to be copersistent in variance. Conditions for copersistence to occur in the linear multivariate GARCH model are presented. These conditions parallel the conditions for linear cointegration in the mean. A simple empirical example with foreign exchange rate data illustrates the ideas. Copyright 1993 by The Econometric Society.

A two-person game is of conflicting interests if the strategy to which player one would most like to commit herself holds player two down to his minimax payoff. Suppose there is a positive prior probability that player one is a "commitme nt type" who will always play this strategy. Then player one will get a t least her commitment payoff in any Nash equilibrium of the repeated game if her discount factor approaches one. This result is robust against further perturbations of the informational structure and in striking contrast to the message of the Folk theorem for games with incomplete information. Copyright 1993 by The Econometric Society.