Liquidity preference and information

This paper explores the link between anticipated information and a preference for liquidity in investment choices. Given a subjective ordering of investment portfolios by their liquidity, we identify a sufficient condition under which the prospect of finer resolution of uncertainty creates a preference for more liquid positions. We then show how this condition might arise naturally in some standard classes of sequential decision problems

Complexity of Manipulative Actions When Voting with Ties

Most of the computational study of election problems has assumed that each voter's preferences are, or should be extended to, a total order. However in practice voters may have preferences with ties. We study the complexity of manipulative actions on elections where voters can have ties, extending the definitions of the election systems (when necessary) to handle voters with ties. We show that for natural election systems allowing ties can both increase and decrease the complexity of manipulation and bribery, and we state a general result on the effect of voters with ties on the complexity of control.Comment: A version of this paper will appear in ADT-201

The Price of Flexibility: Towards a Theory of Thinking Aversion

The goal of this paper is to model an agent who dislikes large choice sets because of the "cost of thinking" involved in choosing from them. We take as a primitive a preference relation over lotteries of menus and impose novel axioms that allow us to separately identify the genuine preference over the content of menus, and the cost of choosing from them. Using this, we formally define the notion of thinking aversion, much in line with the definitions of risk or ambiguity aversion. We represent such preference as the difference between a monotone and affine evaluation of the content of the set and an anticipated thinking cost function that assigns to each set a thinking cost. We further extend this characterization to the case of monotonicity of the genuine rank and introduce a measure of comparative thinking aversion. Finally, we propose behavioral axioms that guarantee that the cost of thinking can be represented as the sum of the cost to find the optimal choice in a set and the cost to find out which is the optimal choice.Cost of Thinking, Contemplation Cost, Bounded Rationality, Preference Over Menus, Preference for Flexibility, Choice overload

On the Hardness of Bribery Variants in Voting with CP-Nets

We continue previous work by Mattei et al. (Mattei, N., Pini, M., Rossi, F., Venable, K.: Bribery in voting with CP-nets. Ann. of Math. and Artif. Intell. pp. 1--26 (2013)) in which they study the computational complexity of bribery schemes when voters have conditional preferences that are modeled by CP-nets. For most of the cases they considered, they could show that the bribery problem is solvable in polynomial time. Some cases remained open---we solve two of them and extend the previous results to the case that voters are weighted. Moreover, we consider negative (weighted) bribery in CP-nets, when the briber is not allowed to pay voters to vote for his preferred candidate.Comment: improved readability; identified Cheapest Subsets to be the enumeration variant of K.th Largest Subset, so we renamed it to K-Smallest Subsets and point to the literatur; some more typos fixe

Computational Complexity in Additive Hedonic Games

We investigate the computational complexity of several decision problems in hedonic coalition formation games and demonstrate that attaining stability in such games remains NP-hard even when they are additive. Precisely, we prove that when either core stability or strict core stability is under consideration, the existence problem of a stable coalition structure is NP-hard in the strong sense. Furthermore, the corresponding decision problems with respect to the existence of a Nash stable coalition structure and of an individually stable coalition structure turn out to be NP-complete in the strong sense