Fragility of information cascades: an experimental study using elicited beliefs

This paper examines the occurrence and fragility of information cascades in two laboratory experiments. One group of low informed participants sequentially guess which of two states has been randomly chosen. In a matched pairs design, another group of high informed participants make similar guesses after having observed the guesses of the low informed participants. In the second experiment, participants’ beliefs about the chosen state are elicited. In equilibrium, low informed players who observe an established pattern of identical guesses herd without regard to their private information whereas high informed players always guess according to their private information. Equilibrium behavior implies that information cascades emerge in the group of low informed participants, the belief based solely on cascade guesses is stationary, and information cascades are systematically broken by high informed participants endowed with private information contradicting the cascade guesses. Experimental results show that the behavior of low informed participants is qualitatively in line with the equilibrium prediction. Information cascades often emerge in our experiments. The tendency of low informed participants to engage in cascade behavior increases with the number of identical guesses. Our main finding is that information cascades are not fragile. The behavior of high informed participants differs markedly from the equilibrium prediction. Only one-third of laboratory cascades are broken by high informed participants endowed with private information contradicting the cascade guesses. The relative frequency of cascade breaks is 15% for the situations where five or more identical guesses are observed. Participants’ elicited beliefs are strongly consistent with their own behavior and show that, unlike in equilibrium, the more cascade guesses participants observe the more they believe in the state favored by those guesses.     

Aggregate information cascades

We introduce a new model of aggregate information cascades where only one of two possible actions is observable to others. Agents make a binary decision in sequence. The order is random and agents are not aware of their own position in the sequence. When called upon, they are only informed about the total number of others who have chosen the observable action before them. This informational structure arises naturally in many applications. Our most important result is that only one type of cascade arises in equilibrium, the aggregate cascade on the observable action. A cascade on the unobservable action never arises.     

Centralized institutions and cascades

Why do sudden and massive social, economic, and political changes occur when and where they do? Are there institutional preconditions that encourage such changes when present and discourage such changes when absent? I employ a general model which suggests that cascades which induce massive equilibrium changes are more likely to occur in regimes with centralized coercive power, defined as the ability to impose more than one type of sanction (economic, legal, political, social, or religious). Centralized authorities are better able to suppress subversive actions when external shocks are small, as citizens have little incentive to incur numerous types of sanctions. However, citizens are also more likely to lie about their internal preferences in such regimes (e.g., falsely declare loyalty to an oppressive government), entailing that larger shocks are more likely to trigger a cascade to a vastly different equilibrium. The model is applied to the severity of protests that followed austerity measures taken in developing nations since the 1970s.     

Equilibrium Unemployment Rate and Customs Union

This paper utilizes the macroeconomics concept of the equilibrium rate of unemployment for theorems on free trade and the formation of customs union. The notion of an equilibrium rate of unemployment appears in the literature on labour, macroeconomics, business cycles and trade theory. Such an equilibrium rate can be derived in a number of ways, for example, by introducing labor–leisure choice in the utility functions of the workers; a labor turnover model and/or by introducing shirking. We extend the two sector-two factor Heckscher–Ohlin–Samuelson model for a small open economy by relaxing the assumption of inelastic labor supply. Specifically, we consider the classical labor supply function obtained from the representative consumer's utility maximisation problem. This consideration allows for the existence of unemployment and we analyse the effects trade policies have on the equilibrium unemployment rate. Given the movement towards free trade (either via the implementation of GATT and/or formation of customs union) it is important to examine its implications for the equilibrium rate of unemployment.     

Limited Depth of Reasoning and Failure of Cascade Formation in the Laboratory

We examine the robustness of information cascades in laboratory experiments. Apart from the situation in which each player can obtain a signal for free (as in the experiment by Anderson and Holt (1997) , American Economic Review , 87 (5), 847–862), the case of costly signals is studied where players decide whether or not to obtain private information, at a small but positive cost. In the equilibrium of this game, only the first player buys a signal and makes a decision based on this information whereas all following players do not buy a signal and herd behind the first player. The experimental results show that too many signals are bought and the equilibrium prediction performs poorly. To explain these observations, the depth of the subjects' reasoning process is estimated, using a statistical error-rate model. Allowing for different error rates on different levels of reasoning, we find that the subjects' inferences become significantly more noisy on higher levels of the thought process, and that only short chains of reasoning are applied by the subjects.     

INFORMATIONAL CASCADES ELICIT PRIVATE INFORMATION*

We introduce cheap talk in a dynamic investment model with information externalities. We first show how social learning adversely affects the credibility of cheap talk messages. Next, we show how an informational cascade makes truth‐telling incentive compatible. A separating equilibrium only exists for high‐surplus projects. Both an investment subsidy and an investment tax can increase welfare. The more precise the sender's information, the higher her incentives to truthfully reveal her private information.     

Sequential voting with abstention

Dekel and Piccione [2000. Sequential voting procedures in symmetric binary elections. J. Polit. Economy 108, 34–55] have proven that information cascades do not necessarily affect the properties of information aggregation in sequential elections: under standard conditions, any symmetric equilibrium of a simultaneous voting mechanism is also an equilibrium of the correspondent sequential mechanism. We show that when voters can abstain, these results are sensitive to the introduction of an arbitrarily small cost of voting: the set of equilibria in the two mechanisms are generally disjoint; and the informative properties of the equilibrium sets can be ranked. If an appropriate q-rule is chosen, when the cost of voting is small the unique symmetric equilibrium of the simultaneous voting mechanism dominates all equilibria of the sequential mechanism.     

A note on external habits and efficiency in the AK model

This paper examines the implications for equilibrium efficiency of alternative formulations of habit formation in the AK model with external habits. Agent’s utility depends on how her current consumption compares to a reference consumption level—the habits stock—determined by average past consumption in the economy. We first prove that perfect substitutability between consumption and habits along the equilibrium path is necessary and sufficient for efficiency. Then, we prove that the competitive equilibrium is efficient if and only if habits enter utility in a subtractive form.     

Are more risk averse agents more optimistic? Insights from a rational expectations model

We analyse a model of partially revealing, rational expectations equilibrium with diverse information, endogenous beliefs formation and uncertain distribution of risk aversion. More risk averse agents are then more optimistic. Such a positive correlation is important for collective decision analysis.     

A MODEL OF BUREAUCRACY AND CORRUPTION*

We analyze bureaucracy and corruption in a market with decentralized exchange and “lemons.” Exchange is modeled as a sequence of bilateral, random matches. Agents have private information about the quality of goods they produce and can supplement trade with socially inefficient bribes. Bureaucracy is modeled as a group of agents who enjoy centralized production and consumption. Transaction patterns between the bureaucracy and the private sector are fully endogenous. Centralized production and consumption in the bureaucracy give rise to low power incentives for the individual bureaucrats. As a result, private agents might bribe bureaucrats, whereas they do not bribe each other. An equilibrium with corruption and an equilibrium without corruption can coexist. We discuss some welfare implications of the model.     

Transaction costs and informational cascades in financial markets

We study the effect of transaction costs (e.g., a trading fee or a transaction tax, like the Tobin tax) on the aggregation of private information in financial markets. We implement a financial market with sequential trading and transaction costs in the laboratory. According to theory, eventually all traders neglect their private information and abstain from trading (i.e., a no-trade informational cascade occurs). We find that, in the experiment, informational no-trade cascades occur when theory predicts they should (i.e., when the trade imbalance is sufficiently high). At the same time, the proportion of subjects irrationally trading against their private information is smaller than in a financial market without transaction costs. As a result, the overall efficiency of the market is not significantly affected by the presence of transaction costs.     

Speculative Attacks with Multiple Sources of Public Information*

We propose a speculative attack model in which agents receive multiple public signals. Diverse pieces of public information can be taken into account differently by different players and are likely to lead to different appreciations ex post. This process defines players' expected private values of a successful attack. The main result shows that equilibrium uniqueness depends on two conditions: (i) signals are sufficiently dispersed and (ii) private beliefs about signals' relative precision differ sufficiently. We derive some implications for information dissemination policy. Transparency in this context is multidimensional: it concerns the publicity of announcements, the number of signals disclosed and their precision.     

Endogenous R&D networks when labour unions have preferences over wages and employment

We develop a model to analyse the pattern of R&D network formation when unions have relative preferences over wages and employment. Within a three-firm industry, we show that when the unions place a low weight on wages and technological spillovers are low, a partial R&D network that includes two firms but excludes the third emerges in equilibrium. In contrast, when the unions care a lot about wages, a complete R&D network that includes all firms emerges. For all other intermediate levels of union preferences over wages, there is no strong stable equilibrium network. Empirical implications emerge from these findings, which are also discussed.     

Social learning in a changing world

Summary. In the social learning model of Banerjee [1] and Bikhchandani, Hirshleifer and Welch [2] individuals take actions sequentially after observing the history of actions taken by the predecessors and an informative private signal. If the state of the world is changing stochastically over time during the learning process, only temporary informational cascades – situations where socially valuable information is wasted – can arise. Furthermore, no cascade ever arises when the environment changes in a sufficiently unpredictable way. Received: December 5, 1996; revised version: February 11, 1997     

Taking the road less traveled by: Does conversation eradicate pernicious cascades?

We offer a model in which sequences of individuals often converge upon poor decisions and are prone to fads, despite communication of the payoff outcomes from past choices. This reflects both direct and indirect action-based information externalities. In contrast with previous cascades literature, cascades here are spontaneously dislodged and in general have a probability less than one of lasting forever. Furthermore, the ability of individuals to communicate can reduce average decision accuracy and welfare.     

Public capital, asymmetric information, and economic growth

Abstract.  We investigate the provision of public capital in an endogenous growth model with asymmetric information. In a credit market with costly screening, we show that the equilibrium contracts are characterized by the self‐selection of borrowers. Through identifying an additional adverse effect of taxation on growth, we show that the optimal tax rate in our model is smaller than the output elasticity of public capital. Therefore, our analysis justifies a more conservative tax policy in the presence of asymmetric information. Furthermore, our model suggests a number of implications that appear to be well supported by preliminary evidence in cross‐country data. JEL classification: D82, H21, O41     

Rich Nations, Poor Nations: How Much Can Multiple Equilibria Explain?

This paper asks whether the income gap between rich and poor nations can be explained by multiple equilibria. We explore the quantitative implications of a simple two-sector general equilibrium model that gives rise to multiplicity, and calibrate the model for 127 countries. Under the assumptions of the model, around a quarter of the world’s economies are found to be in a low output equilibrium. We also find that, since the output gains associated with an equilibrium switch are sizeable, the model can explain between 15 and 25% of the variation in the logarithm of GDP per worker across countries.     

An Experiment to Evaluate Bayesian Learning of Nash Equilibrium Play

We report on an experiment designed to evaluate the empirical implications of Jordan's model of Bayesian learning in games of incomplete information. A finite example is constructed in which the model generates unique predictions of subjects' choices in nearly all periods. When the “true” game defined by players' private information was one with a unique equilibrium in pure strategies, the experimental subjects' play converged to the equilibrium, as Jordan's theory predicts, even when the subjects had not attained complete information about one another. But when there were two pure strategy equilibria, the theory's predictions were not consistent with observed behavior. Journal of Economic Literature Classification numbers: D83, C72, C92.     

On social norms and beliefs: A model of manager environmental behavior

A prevailing view in the literature states that social sanctions can support, in equilibrium, high levels of obedience to a costly norm. The reason is that social disapproval and stigmatization faced by the disobedient are highest when disobedience is the exception rather than the rule in society. In contrast, the Bayesian model introduced here shows that, imperfect information causes the expected social sanction to be lowest precisely when obedience is more common. This, amongst other findings, draws a distinct line between social and moral norms, both of which may depend on others’ behavior but not on action observability. The implications of the use of non-Bayesian belief formation rules by society, namely a representativeness rule (overweighting the signals) and conservativism (overweighting the prior), for payoff functions and equilibria are explored.     

Disclosure of information in matching markets with non-transferable utility

We present a model of two-sided matching where utility is non-transferable and information about individualsʼ skills is private, utilities are strictly increasing in the partnerʼs skill and satisfy increasing differences. Skills can be either revealed or kept hidden, but while agents on one side have verifiable skills, agents on the other side have skills that are unverifiable unless certified, and certification is costly. Agents who have revealed their skill enter a standard matching market, while others are matched randomly. We find that in equilibrium only agents with skills above a cutoff reveal, and then they match assortatively. We show that an equilibrium always exists, and we discuss multiplicity. Increasing differences play an important role to shape equilibria, and we remark that this is unusual in matching models with non-transferable utility. We close the paper with some comparative statics exercises where we show the existence of non-trivial externalities and welfare implications.