POLICY WITH DISPERSED INFORMATION

Information regarding economic fundamentals is widely dispersed in society, is only imperfectly aggregated through prices or other indicators of aggregate activity, and cannot be centralized by the government or any other institution. In this paper we seek to identify policies that can improve the decentralized use of such dispersed information without requiring the government to observe this information. We show that this can be achieved by appropriately designing the contingency of taxation on ex post public information regarding the realized fundamentals and aggregate activity. When information is common (as in the Ramsey literature) or when agents have private information only about idiosyncratic shocks (as in the Mirrlees literature), the contingency on fundamentals alone suffices for efficiency. When instead agents have private information about aggregate shocks, the contingency on aggregate activity is crucial. An appropriate combination of the two contingencies permits the government to: (i) dampen the impact of noise and hence reduce non-fundamental volatility, without also dampening the impact of fundamentals; (ii) induce agents to internalize informational externalities, and hence improve the speed of social learning; (iii) restore a certain form of constrained efficiency in the decentralized use of information; and (iv) guarantee that welfare increases with the provision of any additional information. (JEL: C72, D62, D82)     

A generalisation of T‐optimality for discriminating between competing models with an application to pharmacokinetic studies

The T‐optimality criterion is used in optimal design to derive designs for model selection. To set up the method, it is required that one of the models is considered to be true. We term this local T‐optimality. In this work, we propose a generalisation of T‐optimality (termed robust T‐optimality) that relaxes the requirement that one of the candidate models is set as true. We then show an application to a nonlinear mixed effects model with two candidate non‐nested models and combine robust T‐optimality with robust D‐optimality. Optimal design under local T‐optimality was found to provide adequate power when the a priori assumed true model was the true model but poor power if the a priori assumed true model was not the true model. The robust T‐optimality method provided adequate power irrespective of which model was true. The robust T‐optimality method appears to have useful properties for nonlinear models, where both the parameter values and model structure are required to be known a priori, and the most likely model that would be applied to any new experiment is not known with certainty. Copyright © 2012 John Wiley & Sons, Ltd.     

Dynamic Mechanism Design: A Myersonian Approach

We study mechanism design in dynamic quasilinear environments where private information arrives over time and decisions are made over multiple periods. We make three contributions. First, we provide a necessary condition for incentive compatibility that takes the form of an envelope formula for the derivative of an agent's equilibrium expected payoff with respect to his current type. It combines the familiar marginal effect of types on payoffs with novel marginal effects of the current type on future ones that are captured by “impulse response functions.” The formula yields an expression for dynamic virtual surplus that is instrumental to the design of optimal mechanisms and to the study of distortions under such mechanisms. Second, we characterize the transfers that satisfy the envelope formula and establish a sense in which they are pinned down by the allocation rule (“revenue equivalence”). Third, we characterize perfect Bayesian equilibrium‐implementable allocation rules in Markov environments, which yields tractable sufficient conditions that facilitate novel applications. We illustrate the results by applying them to the design of optimal mechanisms for the sale of experience goods (“bandit auctions”).     

Dynamic Global Games of Regime Change: Learning,Multiplicity, and the Timing of Attacks

Global games of regime change—coordination games of incomplete information in which a status quo is abandoned once a sufficiently large fraction of agents attack it—have been used to study crises phenomena such as currency attacks, bank runs, debt crises, and political change. We extend the static benchmark examined in the literature by allowing agents to take actions in many periods and to learn about the underlying fundamentals over time. We first provide a simple recursive algorithm for the characterization of monotone equilibria. We then show how the interaction of the knowledge that the regime survived past attacks with the arrival of information over time, or with changes in fundamentals, leads to interesting equilibrium properties. First, multiplicity may obtain under the same conditions on exogenous information that guarantee uniqueness in the static benchmark. Second, fundamentals may predict the eventual fate of the regime but not the timing or the number of attacks. Finally, equilibrium dynamics can alternate between phases of tranquility—where no attack is possible—and phases of distress—where a large attack can occur—even without changes in fundamentals.     

The Role of Career Choice in Understanding Job Mobility

This paper presents a simple model that explains how the likelihood of job changes and their complexity changes over a worker's career, and the empirical work presented here uses the life cycle patterns of mobility and their complexity to infer the relative importance of firm‐specific versus career‐specific concerns as determinants of mobility decisions. The estimates of the model indicate that the contemporaneous presence of two quality matches, one career‐specific and one firm‐specific, is necessary to understand the patterns of the data. The model also predicts that the welfare losses implied by a disappearance of a career can be on average twice as large as the losses implied by a plant closure.     

Efficient Use of Information and Social Value of Information

This paper analyzes equilibrium and welfare for a tractable class of economies (games) that have externalities, strategic complementarity or substitutability, and heterogeneous information. First, we characterize the equilibrium use of information: complementarity heightens the sensitivity of equilibrium actions to public information, raising aggregate volatility, whereas substitutability heightens the sensitivity to private information, raising cross‐sectional dispersion. Next, we define and characterize an efficiency benchmark designed to address whether the equilibrium use of information is optimal from a social perspective; the efficient use of information reflects the social value of aligning choices across agents. Finally, we examine the comparative statics of equilibrium welfare with respect to the information structure; the social value of information is best understood by classifying economies according to the inefficiency, if any, in the equilibrium use of information. We conclude with a few applications, including production externalities, beauty contests, business cycles, and large Cournot and Bertrand games.     

The integrative power of online collective action networks beyond protest. Exploring social media use in the process of institutionalization

Abstract

In this article, we aim at expanding the event-based and protest-centered perspective that is typically adopted to study the nexus between social media and movements. To this aim, we propose a network-based approach to explore the changing role that these tools play during the dynamic unfolding of movement processes and, more particularly, over the course of their institutionalization. In the first part, we read the added value of social media as a function of the ‘integrative power’ of the networks they foster – a unique and evolving form of sociotechnical power that springs from the virtuous encounter between social media networking potential and social resources. In the second part, we investigate this form of power by focusing directly on online networks’ structure as well as on the type of communication and participation environments they host. We apply our proposed approach to the longitudinal exploration of the Twitter networks deployed in the period 2012–2014 during three annual editions of the transnational feminist campaign ‘Take Back The Tech!’ (TBTT). Results from our case study suggest that, over time, TBTT supporters do in fact make a differentiated use of social media affordances – progressively switching their communicative strategies to better sustain the campaign’s efforts inside and outside institutional venues. Thus, the exploration of the TBTT case provides evidence of the usefulness of the proposed approach to reflect on the different modes in which social media can be exploited in different mobilization stages and political terrains.