Knowledge that Transforms

This paper considers asymptotically efficient instrumental variables estimation of nonlinear models in an i.i.d. environment. The class of models includes nonlinear simultaneous equations models and other models of interest. A problem in constructing efficient instrumental variables estimators for such models is that the optimal instruments involve a conditional expectation, calculation of which can require functional form assumptions for the conditional distribution of endogenous variables, as well as integration. Nonparametric methods provide a way of avoiding this difficulty. Here it is shown that nonparametric estimates of the optimal instruments can give asymptotically efficient instrumental variables estimators. Also, ways of choosing the nonparametric estimate in applications are discussed. Two types of nonparametric estimates of the optimal instruments are considered. Each involves nonparametric regression, one by nearest neighbor and the other by series approximation. The finite sample properties of the estimators are considered in a small sampling experiment involving an endogenous dummy variable model.

IN AN IMPORTANT recent contribution, Persson, Persson, and Svensson (1987) (hereafter PPS) suggest that through careful restructuring of its nominal and real debt obligations, a government may be able to induce future governments to follow the monetary and fiscal policies that it regards as optimal today. The PPS argument builds on Lucas and Stokey's (1983) demonstration that in a special nonmonetary setting, the time inconsistency of optimal fiscal policy can be avoided through managing the term structure of real government obligations to the public. The basic idea of the PPS scheme for monetary economies is disarmingly intuitive: in addition to continually restructuring nominal and real debt obligations a la Lucas-Stokey, each government must ensure that the next government inherits a stream of nominal claims on the public whose present discounted value equals the stock of money. This equality, PPS argue, removes the incentive for surprise inflation or deflation, because such surprises would not affect the real net worth of the government. This note shows that the PPS prescription for avoiding time inconsistency, appealing as it is, is not generally sufficient. Even under the debt restructuring they recommend, optimal policy is likely to be time inconsistent. The main reason why their scheme fails is that the restrictions it imposes on government asset stocks satisfy first-order but not second-order conditions for an optimum. Because of the complex interactions between the current price level and future interest rates, a government can raise its objective function by moving several variables at once away from the levels planned by the previous government, even though price-level changes alone would not affect government net worth. We develop our argument using the model, notation, and equation numbers of PPS, to which the reader is referred for details. The maximization problem associated with

This paper describes a new approach to normative economics, combining the theory of social choice with econometric modeling of aggregate consumer behavior. The author first derives a system of aggregate demand functions by exact aggregation over individual demand functions. He then constructs measures of individual welfare from systems of individual demand functions. Finally, the author incorporates these measures into a social welfare function, introducing ethical assumptions based on horizontal and vertical equity. To illustrate the application of this approach, he considers the U.S. standard of living and its cost over the period 1947-85. Copyright 1990 by The Econometric Society.

In this paper, the authors reexamine the data from B. O'Neill's (1987) experiment involving a repeated, two-person, constant-sum game. They find that there is less evidence in support of the minimax hypothesis than indicated by O'Neill. There is strong evidence of serial correlation in players' choices, with several players displaying statistically significant dependence on the past moves of their opponents. The authors interpret this finding as evidence that the plays themselves rejected minimax play as the appropriate model for their opponents' behavior. They find no evidence that players' behavior approached minimax behavior as players became more experienced. Copyright 1990 by The Econometric Society.

This paper analyzes a competitive credit market where banks use imperfect and independent tests to assess the ability of a potential creditor to repay credit. The banks compete by announcing interest rates at which they will provide credit to those applicants who pass the banks' tests. The proportion of applicants who pass the test of at least one bank increases with the number of banks providing credit, so the average credit-worthiness decreases. It is then shown that in a situation where all banks charge the same interest rate, a bank always has the incentive to undercut in order to improve the average credit-worthiness of its own clientele. This feature represents the major difference from the situations in standard Bertrand and Bertrand-Edgeworth models. Copyright 1990 by The Econometric Society.

Asymptotic distributions are derived for the ordinary least squares estimate of a first order autoregression model when the series is fractionally integrated. The fractional unit root distribution is introduced to describe the limiting distribution. The unit root distribution is shown to be an atypical member of this family because its density is nonzero over the entire real line. For -1/2 Copyright 1990 by The Econometric Society.

Preference relations over two-stage lotteries are analyzed. Empirical evidence indicates that decisionmakers do not always behave in accordance with the reduction of compound lotteries axiom, but they seem to satisfy a compound independence axiom. Although the reduction and the compound independence axioms, together with continuity, imply expected utility theory, each of them by itself is compatible with all possible preference relations over simple lotteries. Using these axioms, the author analyzes three different versions of expected utility for two-stage lotteries. The author suggests several different compound dominance axioms as possible replacements of the reduction axiom, which are strictly weaker than the reduction of compound lotteries axiom. Copyright 1990 by The Econometric Society.

We analyze a model of optimal consumption and portfolio selection in which consumption services are generated by holding a durable good. The durable good is illiquid in that a transaction cost must be paid when the good is sold. It is shown that optimal consumption is not a smooth function of wealth; it is optimal for the consumer to wait until a large change in wealth occurs before adjusting his consumption. As a consequence, the consumption based capital asset pricing model fails to hold. Nevertheless, it is shown that the standard, one factor, market portfolio based capital asset pricing model does hold in this environment. It is shown that the optimal durable level is characterized by three numbers (not random variables), say x, y, and z (where x

The paper presents a simple pairwise meetings model of trade.The new feature is that agents have asymmetric information about the true state of the world.The focus is on the transmission of the information through the process of trade.The qualitative questions is: to what extent is the information revealed to uninformed agents through the trading process, when the market is in some sense frictionless?In particular: does the decentralized process give rise to full revelation results as derived by the literature on rational expectations for centralized and competitive environments?In the context of the model of this paper, it turns out that the information is not fully revealed to uninformed agents, even when the market is in some sense approximately frictionless.