81 research outputs found
Plurality Voting under Uncertainty
Understanding the nature of strategic voting is the holy grail of social
choice theory, where game-theory, social science and recently computational
approaches are all applied in order to model the incentives and behavior of
voters.
In a recent paper, Meir et al.[EC'14] made another step in this direction, by
suggesting a behavioral game-theoretic model for voters under uncertainty. For
a specific variation of best-response heuristics, they proved initial existence
and convergence results in the Plurality voting system.
In this paper, we extend the model in multiple directions, considering voters
with different uncertainty levels, simultaneous strategic decisions, and a more
permissive notion of best-response. We prove that a voting equilibrium exists
even in the most general case. Further, any society voting in an iterative
setting is guaranteed to converge.
We also analyze an alternative behavior where voters try to minimize their
worst-case regret. We show that the two behaviors coincide in the simple
setting of Meir et al., but not in the general case.Comment: The full version of a paper from AAAI'15 (to appear
Equilibrium in Labor Markets with Few Firms
We study competition between firms in labor markets, following a
combinatorial model suggested by Kelso and Crawford [1982]. In this model, each
firm is trying to recruit workers by offering a higher salary than its
competitors, and its production function defines the utility generated from any
actual set of recruited workers. We define two natural classes of production
functions for firms, where the first one is based on additive capacities
(weights), and the second on the influence of workers in a social network. We
then analyze the existence of pure subgame perfect equilibrium (PSPE) in the
labor market and its properties. While neither class holds the gross
substitutes condition, we show that in both classes the existence of PSPE is
guaranteed under certain restrictions, and in particular when there are only
two competing firms. As a corollary, there exists a Walrasian equilibrium in a
corresponding combinatorial auction, where bidders' valuation functions belong
to these classes.
While a PSPE may not exist when there are more than two firms, we perform an
empirical study of equilibrium outcomes for the case of weight-based games with
three firms, which extend our analytical results. We then show that stability
can in some cases be extended to coalitional stability, and study the
distribution of profit between firms and their workers in weight-based games
Contract Design for Energy Demand Response
Power companies such as Southern California Edison (SCE) uses Demand Response
(DR) contracts to incentivize consumers to reduce their power consumption
during periods when demand forecast exceeds supply. Current mechanisms in use
offer contracts to consumers independent of one another, do not take into
consideration consumers' heterogeneity in consumption profile or reliability,
and fail to achieve high participation.
We introduce DR-VCG, a new DR mechanism that offers a flexible set of
contracts (which may include the standard SCE contracts) and uses VCG pricing.
We prove that DR-VCG elicits truthful bids, incentivizes honest preparation
efforts, enables efficient computation of allocation and prices. With simple
fixed-penalty contracts, the optimization goal of the mechanism is an upper
bound on probability that the reduction target is missed. Extensive simulations
show that compared to the current mechanism deployed in by SCE, the DR-VCG
mechanism achieves higher participation, increased reliability, and
significantly reduced total expenses.Comment: full version of paper accepted to IJCAI'1
A Local-Dominance Theory of Voting Equilibria
It is well known that no reasonable voting rule is strategyproof. Moreover,
the common Plurality rule is particularly prone to strategic behavior of the
voters and empirical studies show that people often vote strategically in
practice. Multiple game-theoretic models have been proposed to better
understand and predict such behavior and the outcomes it induces. However,
these models often make unrealistic assumptions regarding voters' behavior and
the information on which they base their vote.
We suggest a new model for strategic voting that takes into account voters'
bounded rationality, as well as their limited access to reliable information.
We introduce a simple behavioral heuristic based on \emph{local dominance},
where each voter considers a set of possible world states without assigning
probabilities to them. This set is constructed based on prospective candidates'
scores (e.g., available from an inaccurate poll). In a \emph{voting
equilibrium}, all voters vote for candidates not dominated within the set of
possible states.
We prove that these voting equilibria exist in the Plurality rule for a broad
class of local dominance relations (that is, different ways to decide which
states are possible). Furthermore, we show that in an iterative setting where
voters may repeatedly change their vote, local dominance-based dynamics quickly
converge to an equilibrium if voters start from the truthful state. Weaker
convergence guarantees in more general settings are also provided.
Using extensive simulations of strategic voting on generated and real
preference profiles, we show that convergence is fast and robust, that emerging
equilibria are consistent across various starting conditions, and that they
replicate widely known patterns of human voting behavior such as Duverger's
law. Further, strategic voting generally improves the quality of the winner
compared to truthful voting
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