Non-myopic learning in differential information economies: the core

Summary. We study the process of learning in a differential information economy, with a continuum of states of nature that follow a Markov process. The economy extends over an infinite number of periods and we assume that the agents behave non-myopically, i.e., they discount the future. We adopt a new equilibrium concept, the non-myopic core. A realized agreement in each period generates information that changes the underlying structure in the economy. The results we obtain serve as an extension to the results in Koutsougeras and Yannelis (1999) in a setting where agents behave non-myopically. In particular, we examine the following two questions: 1) If we have a sequence of allocations that are in an approximate non-myopic core (we allow for bounded rationality), is it possible to find a subsequence that converges to a non-myopic core allocation in a limit full information economy? 2) Given a non-myopic core allocation in a limit full information economy can we find a sequence of approximate non-myopic core allocations that converges to that allocation? Received: May 25, 1999; revised version: August 9, 1999     

Risk Sharing and Information in Village Economies

Arrangements for achieving efficient risk-sharing vary depending on the information available to agents in the economy. The usual Euler equation restricts efficient allocations in an economy which obeys the permanent income hypothesis, while efficient allocations in an economy with private information and long-term contracts satisfy a symmetric restriction, but not the Euler equation. Full insurance arrangements are unique in that they satisfy both restrictions.
We look at an environment in which it seems likely that long-term contracts play a role in mitigating the effects of private information: three village economies in South India. The evidence that consumption allocations satisfy the private information restriction is quite strong for households in two of the three villages; the evidence for the third village suggests that while consumption for some households satisfies the private information restrictions, other households' consumption obey the permanent income hypothesis.     

PRICE‐LEVEL DETERMINATION UNDER DISPERSED INFORMATION AND MONETARY POLICY*

This paper considers the determination of aggregate price level under dispersed information. A Central Bank sets policy in response to its noisy measure of the price level, and each agent makes its decisions by observing a subset of data. Information revealed to the agents and the bank is determined endogenously. It is shown that the aggregate state of the economy is not revealed perfectly to anybody but this economy behaves as if it is a representative‐agent economy in which the representative agent has perfect information while the Bank has partial information. The Bank's information set affects fluctuations in the price level through its effect on policy.     

Interim efficient allocations under uncertainty

This paper considers an exchange economy under uncertainty with asymmetric information. Uncertainty is represented by multiple priors and posteriors of agents who have either Bewley's incomplete preferences or Gilboa-Schmeidler's maximin expected utility preferences. The main results characterize interim efficient allocations under uncertainty; that is, they provide conditions on the sets of posteriors, thus implicitly on the way how agents update the sets of priors, for non-existence of a trade which makes all agents better off at any realization of private information. For agents with the incomplete preferences, the condition is necessary and sufficient, but for agents with the maximin expected utility preferences, the condition is sufficient only. A couple of necessary conditions for the latter case are provided.     

Erratic monetary policy and the dispersion of commodity prices

This paper develops a closed economy macroeconomic model with many goods, where information flows are not instantaneous. Economic agents form rational expectations of future economic variables based on present information, and measure the future price level with a true cost-of-living index that allows for substitutions among commodities as relative prices change. The major inference drawn from our model is that, when information flows are imperfect, an increase in the variance of the money supply injects noise into economic agents forecasts of prices, and increases the equilibrium level of dispersion in commodity prices.     

Monetary Neutrality and Optimality with Symmetric Partial Information

The neutrality and optimality of countercyclical monetary policy are examined in a representative economy featuring competitive equilibria in multiple markets and rational expectations based on a form of private information about current stochastic innovations in the economy. A necessary and sufficient condition for the neutrality of monetary policy is stated in terms of restrictions on the parameters of the linear rule describing prospective monetary feedback. Optimal monetary policy is fully characterized in terms of an alternative set of parameter restrictions. Optimal monetary feedback completely stabilizes deviations in commodity output by eliminating the influence of those current innovations about which agents cannot directly observe from the rational expectations of agents. [311]     

Limited information minimal state variable learning in a medium-scale multi-country model

Rational expectations has been the dominant way to model expectations, but the literature has quickly moved to a more realistic assumption of boundedly rational learning where agents are assumed to use only a limited set of information to form their expectations. A standard assumption is that agents form expectations by using the correctly specified reduced form model of the economy, the minimal state variable solution (MSV), but they do not know the parameters. However, with medium-sized and large models the closed-form MSV solutions are difficult to attain given the large number of variables that could be included. Therefore, agents base expectations on a misspecified MSV solution. In contrast, we assume that agents know the deep parameters of their own optimising frameworks. However, they are not assumed to know the structure nor the parameterisation of the rest of the economy, nor do they know the stochastic processes generating shocks hitting the economy. In addition, agents are assumed to know that the changes (or the growth rates) of fundament variables can be modelled as stationary ARMA(p,q) processes, the exact form of which is not, however, known by agents. This approach avoids the complexities of dealing with a potential vast multitude of alternative misspecified MSVs.Using a new multi-country euro area model with boundedly estimated rationality we show that this approach is compatible with the same limited information assumption that was used in deriving and estimating the behavioural equations of different optimising agents. We find that there are strong differences in the adjustment path to the shocks to the economy when agents form expectations using our learning approach compared to expectations formed under the assumption of strong rationality. Furthermore, we find some variation in expansionary fiscal policy in periods of downturns compared to boom periods.     

Perfect competition in asymmetric information economies: compatibility of efficiency and incentives

The idea of perfect competition for an economy with asymmetric information is formalized via an idiosyncratic signal process in which the private signals of almost every individual agent can influence only a negligible group of agents, and the individual agents’ relevant signals are essentially pairwise independent conditioned on the true states of nature. Thus, there is no incentive for an individual agent to manipulate her private information. The existence of incentive compatible, ex post Walrasian allocations is shown for such a perfectly competitive asymmetric information economy with or without “common values”. Consequently, the conflict between incentive compatibility and Pareto efficiency is resolved exactly, and its asymptotic version is derived for a sequence of large, but finite private information economies.     

The core of an exchange economy with asymmetric information

This paper studies the core of an exchange economy in which agents are asymmetrically informed about states of nature. An agent's information is modelled as part of his consumption set and thus as part of his consumption plans. If an agent joins a coalition, his information changes according to an exogenously given information rule, a concept introduced by B. Allen. It is shown that an exchange economy with asymmetric information generates a well defined cooperative game and that the core of this game and thus the core of the underlying economy is nonempty. In contrast to recent results, this holds independently of the given information rule.     

Trade and revelation of information

We consider an economy with asymmetric information and two types of agents, fully informed and uninformed. Uninformed agents update their information observing equilibrium prices and the equilibrium levels of other agents’ excess demand. We show that, for a generic set of economies, there are rational expectations equilibria which are partially revealing on an open, dense set of signals of positive Lebesgue measure, provided that the dimension of the signal space is sufficiently larger than the dimension of the commodity space.     

新凯恩斯主义粘性信息理论研究评述

为了说明价格粘性与工资粘性产生的微观基础,新凯恩斯主义者近年来提出了粘性信息模型,认为关于宏观经济运行的各种信息在经济主体之间的传播是缓慢的,其原因在于获取信息和处理信息是需要花费成本的,最优化也是需要成本的,虽然价格总是变动的,但企业的价格决策并不是总是以当前最新的信息为基础,这就产生了理性的疏忽。新凯恩斯主义者提出了粘性信息的菲利普斯曲线,认为当前通货膨胀率不仅仅取决于当前产出,还依赖于过去对当前通货膨胀率以及产出缺口变动率的预期。本文认为粘性信息理论是凯恩斯主义理论的一次重大飞跃,对微观经济主体的假设更加系统、更接近现实,克服了完全理性假说非现实性的缺点,对经济活动的解释更具有可信度,是当代宏观经济学的重要进展。     

Incomplete financial markets and differential information

We provide a model of an incomplete markets economy where private restrictions on consumption are interpreted as lack of information. We prove existence of an equilibrium where agents are unable to infer any additional information from prices. When assets are nominal, these non-enlightening equilibrium prices result in a reduction of the degree of real indeterminacy.     

On Ramsey's conjecture: efficient allocations in the neoclassical growth model with private information

In his seminal paper of 1928, Ramsey conjectured that if agents discounted the future differently, in the long run all agents except the most patient would live at the subsistence level. The validity of this conjecture was investigated in different environments. In particular, it has been confirmed in the neoclassical growth model with dynamically complete markets. This paper studies this conjecture in a version of this model that includes private information and heterogeneous agents. A version of Bayesian implementation is introduced and a recursive formulation of the original allocation problem is established. Efficient allocations are renegotiation-proof and the expected utility of any agent cannot go to zero with positive probability if the economy does not collapse. If the economy collapses all agents will get zero consumption forever. Thus, including any degree of private information in the neoclassical growth model will deny Ramsey's conjecture, if efficient allocations are considered.     

Inefficiency caused by random matching and heterogeneity

I study an economy with sellers and buyers with unit supplies and unit demands. Both parties have valuations uniformly distributed on a unit interval. I quantify the inefficiency, compared to the Walrasian markets, when the agents meet randomly. There are several causes of inefficiency that I deal with separately. First, even if there is perfect information about valuations it makes a difference whether all agents participate in the markets or whether only those who would trade in the Walrasian market participate. The same applies when there is private information about valuations.     

Some Aggregate Effects of Heterogeneity in Information Processing

This paper analyzes the equilibrium of an economy where economic agents differ with respect to their information gathering and processing abilities. Our results depend on the magnitude of the relative risk aversion. We show that the unsophisticated (with respect to their information processing abilities) agents are disproportionately important in the cases of both large and small risk aversion. In the case of the relative risk aversion measure being greater than unity volatility of aggregate consumption is reduced. This supports the view that observed consumption in many countries fluctuates less than predicted by models with fully rational agents only.     

Rationally mispriced assets in equilibrium

We present a simple model of trading in a financial market where agents are asymmetrically informed and information is transmitted through the price system. We characterize the equilibrium for this economy and show that ‘rational mispricing’ of assets occurs if the price system fails to reveal the insider information accurately. It is argued that the communication of wrong information through equilibrium prices is compatible with full rationality on the part of the investors and may explain deviations from the efficient markets hypothesis.     

Market Selection and Asymmetric Information

We consider a dynamic general equilibrium asset pricing model with heterogeneous agents and asymmetric information. We show how agents' different methods of gathering information affect their chances of survival in the market depending upon the nature of the information and the level of noise in the economy.     

Endogenous Alleviation of Overreaction Problem by Aggregate Information Announcement

It is well‐known that agents overreact to public information in markets characterized by strategic complementarities. We propose a simple and implementable method of alleviating the overreaction problem. Extending the beauty‐contest game of Morris and Shin to a multi‐region economy, we show that, under an aggregate information announcement, each agent converts purely public information into imperfect public information endogenously. This makes the agents’ beliefs dispersed and alleviates the overreaction problem. Moreover, we compare the welfare effect of the aggregate information announcement with that of a separate announcement. We find that there exist plausible situations where the aggregate information announcement is better than the separate information announcement despite reduced quality.     

Entrepreneurship,Financiership, and Selection*

We develop an equilibrium model of the market for entrepreneurial finance, in which all agents have some personal wealth and a project whose quality is their private information. All agents choose whether to invest either as entrepreneurs or financiers, or to invest in storage technology. We find that a binding economy‐level wealth constraint, which renders credit scarce, can create advantageous selection, where productive agents become entrepreneurs and unproductive agents become their financiers. If funding is easier to obtain, entrepreneurship also attracts unproductive agents. In our model, individual wealth and entrepreneurship are positively (negatively) correlated if financial market participation is complete (incomplete).     

Was the deflation of the depression anticipated? An inference using real-time data

Theories that explain the behavior of the economy during the Depression are based on assumptions about agents’ expectations about future price trends. This paper uses an alternative methodological approach which utilizes real-time information from the Depression period to infer whether deflation was anticipated. The information includes the forecasting methodology of that time as well as projections about anticipated output that were obtained from the textual analysis of business statements, converting qualitative to quantitative data. We infer that deflation was not anticipated because agents did not expect economic output to consistently decrease.