Sudipta Sarangi

Nash networks with heterogeneous links

Abstract A non-cooperative model of network formation is developed. Link formation is one-sided. Information flow is two-way. The model builds on the work of Bala and Goyal who permit links to fail with a certain common probability. In our model the probability of failure can be different for different links. The set of networks which are Nash for suitably chosen model parameters consists of all essential networks. We specifically investigate Nash networks that are connected, super-connected, or stars. Efficiency, Pareto-optimality, and existence issues are discussed through examples. Three alternative model specifications are explored to address potential shortcomings.

Age Effects and Heuristics in Decision Making

Using controlled experiments, we examine how individuals make choices when faced with multiple options. Choice tasks are designed to mimic the selection of health insurance, prescription drug, or retirement savings plans. In our experiment, available options can be objectively ranked, allowing us to examine optimal decision making. First, the probability of a person selecting the optimal option declines as the number of options increases, with the decline being more pronounced for older subjects. Second, heuristics differ by age, with older subjects relying more on suboptimal decision rules. In a heuristics validation experiment, older subjects make worse decisions than younger subjects.

Sensor-centric energy-constrained reliable query routing for wireless sensor networks

Standard wireless sensor network models emphasize energy efficiency and distributed decision-making by considering untethered and unattended sensors. To this we add two constraints--the possibility of sensor failure and the fact that each sensor must tradeoff its own resource consumption with overall network objectives. In this paper, we develop an analytical model of energy-constrained, reliable, data-centric information routing in sensor networks under all the above constraints. Unlike existing techniques, we use game theory to model intelligent sensors thereby making our approach sensor-centric. Sensors behave as rational players in an N-player routing game, where they tradeoff individual communication and other costs with network wide benefits. The outcome of the sensor behavior is a sequence of communication link establishments, resulting in routing paths from reporting to querying sensors. We show that the optimal routing architecture is the Nash equilibrium of the N-player routing game and that computing the optimal paths (which maximizes payoffs of the individual sensors) is NP-Hard with and without data-aggregation. We develop a game-theoretic metric called path weakness to measure the qualitative performance of different routing mechanisms. This sensor-centric concept which is based on the contribution of individual sensors to the overall routing objective is used to define the quality of routing (QoR) paths. Analytical results on computing paths of bounded weakness are derived and game-theoretic heuristics for finding approximately optimal paths are presented. Simulation results are used to compare the QoR of different routing paths derived using various energy-constrained routing algorithms.

Sensor-centric quality of routing in sensor networks

Standard embedded sensor network models emphasize energy efficiency and distributed decision-making by considering untethered and unattended sensors. To this we add two constraints - the possibility of sensor failure and the fact that each sensor must tradeoff its own resource consumption with overall network objectives. In this paper, we develop an analytical model of data-centric information routing in sensor networks under all the above constraints. Unlike existing techniques, we use game theory to model intelligent sensors thereby making our approach sensor-centric. Sensors behave as rational players in an N-player routing game, where they tradeoff individual communication and other costs with network wide benefits. The outcome of the sensor behavior is a sequence of communication link establishments, resulting in routing paths from reporting to querying sensors. We show that the optimal routing architecture is the Nash equilibrium of the N-player routing game and that computing the optimal paths (which maximizes payoffs of the individual sensors) is NP-hard with and without data-aggregation. We develop a game-theoretic metric called path weakness to measure the qualitative performance of different routing mechanisms. This sensor-centric concept which is based on the contribution of individual sensors to the overall routing objective is used to define the quality of routing (QoR) paths. Simulation results are used to compare the QoR of different routing paths derived using various energy-constrained routing algorithms.

The Economics of Microfinance

The microfinance revolution, begun with independent initiatives in Latin America and South Asia starting in the 1970s, has so far allowed 65 million poor people around the world to receive small loans without collateral, build up assets, and buy insurance. This comprehensive survey of microfinance seeks to bridge the gap in the existing literature on microfinance between academic economists and practitioners. Both authors have pursued the subject not only in academia but in the field; Beatriz Armendariz founded a microfinance bank in Chiapas, Mexico, and Jonathan Morduch has done fieldwork in Bangladesh, China, and Indonesia. The book provides an overview of microfinance by addressing a range of issues, including lessons from informal markets, savings and insurance, the role of women, the place of subsidies, impact measurement, and management incentives. It integrates theory with empirical data, citing studies from Asia, Africa, and Latin America and introducing ideas about asymmetric information, principal-agent theory, and household decision making in the context of microfinance.

No return, no refund: an analysis of deposit-refund systems

Firms and governments in developed economies frequently employ deposit-refund systems to promote return and reuse of product packages and containers. We analyze a model of monopoly facing heterogeneous consumers in which recycling (package return by consumers) generates an external benefit. It is shown that when consumer’s preferences over recycling differ, the monopolist can price discriminate between consumers leading to socially suboptimal recycling. In the absence of any externalities, the analysis can be viewed as a model of couponsor mail-in rebateswhich work as price-discrimination devices. The role of government subsidies and additional deposits to eliminate suboptimal recycling is also analyzed. Finally, the model is extended to incorporate hustling, i.e., allowing consumers to recycle packages discarded by other consumers.

Stable Networks and Convex Payoffs

Recently a variety of link-based stability concepts have emerged in the literature on game theoretic models of social network formation. We investigate two basic formation properties that establish equivalence between some well known types of stable networks and their natural extensions. These properties can be identified as convexity conditions on the network payoff structures.

Games in Fuzzy Environments

A noncooperative model of a normal form game is developed using tools from fuzzy set theory. The paper extends the decision theory framework of Bellman and Zadeh (1970) to a game-theoretic setting. We identify conditions for the existence of equilibrium in this setting and provide a duopoly example. The paper also provides a review of the existing literature on noncooperative fuzzy games and their applications.

Fuzzy pair-wise dominance and fuzzy indices: An evaluation of productive performance

Abstract Usually, efficiency measurement and evaluation are based on the definition of a frontier that envelops the observed production plans. Measurement and evaluation of productive performance is also achieved with the concept of pair-wise dominance that does not require the existence of a frontier along with the required technological assumptions needed for its definition. In situations where measurement inaccuracies occur, the traditional assumption of crisp production plans can be substituted with the alternative assumption of fuzzy production plans as proposed by fuzzy set theory. This research presents indices that capture the degree to which pair-wise dominance occurs between two fuzzy production plans. The proposed approach is based on the various comparison indices known from the literature that are used to compare fuzzy intervals and is compared with an earlier fuzzy pair-wise classification scheme. Finally, the approach is used to evaluate the productive performance of suspect production plans from the preprint insertion manufacturing process.

Reducing Choice Overload without Reducing Choices

Previous studies have demonstrated that a multitude of options can lead to choice overload, reducing decision quality. Through controlled experiments, we examine sequential choice architectures that enable the choice set to remain large while potentially reducing the effect of choice overload. A specific tournament-style architecture achieves this goal. An alternate architecture in which subjects compare each subset of options to the most preferred option encountered thus far fails to improve performance due to the status quo bias. Subject preferences over different choice architectures are negatively correlated with performance, suggesting that providing choice over architectures might reduce the quality of decisions.