Improving an exact approach for solving separable integer quadratic knapsack problems

We consider the specially structured (pure) integer Quadratic Multi-Knapsack Problem (QMKP) tackled in the paper “Exact solution methods to solve large scale integer quadratic knapsack problems” by D. Quadri, E. Soutif and P. Tolla (2009), recently appeared on this journal, where the problem is solved by transforming it into an equivalent 0–1 linearized Multi-Knapsack Problem (MKP). We show that, by taking advantage of the structure of the transformed (MKP), it is possible to derive an effective variable fixing procedure leading to an improved branch-and-bound approach. This procedure reduces dramatically the resulting linear problem size inducing an impressive improvement in the performances of the related branch and bound approach when compared to the results of the approach proposed by D. Quadri, E. Soutif and P. Tolla.     

Egalitarianism and utilitarianism in committees of representatives

We consider a committee of representatives that makes dichotomous choices (acceptance/rejection) by vote. Given the size of each group represented, what is the most adequate voting rule for the committee? We provide answers based on each of the two principles commonly used to make normative assessments in different contexts: egalitarianism and utilitarianism. To that end, we introduce utilities into the model and adopt a normative approach.     

Educating for Practice in the Chicano Community

This paper conveys one perspective on the development and implementation of a training curriculum designed within a framework of knowledge, values, and skills essential for compatible and complementary social work practice in the Chicano community. It reflects the theoretical foundations upon which the Chicano Training Center is constructing a continuing education program for social service and mental health personnel. Curriculum content areas and emphases, as well as training modalities, are discussed and suggested as possible means for educating practitioners to better understand and serve Mexican Americans. The development of bicultural practice models in service delivery systems is also stressed.     

THE LABOR MARKET IN THE ART SECTOR OF BAROQUE ROME

We analyze the labor market for painters in Baroque Rome using unique data on primary sales of portraits, still lifes, genre paintings, landscapes, and figurative paintings. In line with the traditional artistic hierarchy of genres, average price differentials between them were high. The matched painter‐patron nature of the dataset allows us to evaluate the extent to which price heterogeneity is related to unobservable characteristics of painters and patrons. We find that the market allocated artists between artistic genres to the point of equalizing the marginal return of each genre. Residual price differences at the employer level can be explained in terms of incentive mechanisms to induce effort in the production of artistic quality and compensating wage differentials. (JEL C23, D8, J3, Z11)     

Assessing success and decisiveness in voting situations

In this paper we propose a simple model for measuring success or decisiveness in voting situations. For an assessment of these features two inputs are claimed to be necessary: the voting rule and the voters behavior. The voting rule specifies when a proposal is to be accepted or rejected depending on the resulting vote configuration. Voting behavior is summarized by a distribution of probability over the vote configurations. This basic model provides a clear common conceptual basis for reinterpreting different power indices and some related game theoretic notions coherently from a unified point of view.The authors would like to thank to M. Braham, M. Machover, N. Megiddo and F. Steffen, for their comments, and to J. F. Mertens for pointing out a misstatement, in all cases referring to previous versions of this paper. This research has been supported by the DGES of the Spanish Ministerio de Educación y Cultura under project PB96-0247, by the Spanish Ministerio de Ciencia y Tecnología under project BEC2000-0875, and by the Universidad del País Vasco under project UPV/EHU00031.321-HA-7918/2000. The first author also acknowledges the financial support from a postdoctoral grant from the Basque Government (2000–2001) and the Spanish Ministerio de Ciencia y Tecnología under the Ramón y Cajal Program.     

MULTIPLE EQUILIBRIA AND DETERRENCE IN AIRLINE MARKETS

We use a longitudinal dataset from the U.S. airline industry to estimate three different models for entry games with very general forms of heterogeneity between U.S. carriers in airline markets: a simultaneous game with complete information and two sequential games with or without strategic entry deterrence. In a sequential game with entry deterrence, an incumbent decides whether to incur a cost to deter potential entrants. We show that the model with sequential games with strategic deterrence provides the best fit to the data. We conclude that the results reject the hypothesis of a static model and support the hypothesis of the existence of strategic entry deterrence. (JEL L1)     

Livability of Urban Public Spaces in Northern Swedish Cities: The Case of Umeå

This study explores how winter conditions are taken into accountin urban planning in the city of Umeå in northern Sweden. Snowand harsh winter conditions are to some extent considered in urban planning in most northern towns in Sweden. Besides that, snow and ice could also be elements in the city attracting people and contribute to the design of public spaces. Current plans and interviews with planners were complemented with participatory observations. The results show that public spaces designed for both winter and summer seasons are preferred.     

Strongly chordal and chordal bipartite graphs are sandwich monotone

A graph class is sandwich monotone if, for every pair of its graphs G ₁=(V,E ₁) and G ₂=(V,E ₂) with E ₁⊂E ₂, there is an ordering e ₁,…,e _k of the edges in E ₂∖E ₁ such that G=(V,E ₁∪{e ₁,…,e _i }) belongs to the class for every i between 1 and k. In this paper we show that strongly chordal graphs and chordal bipartite graphs are sandwich monotone, answering an open question by Bakonyi and Bono (Czechoslov. Math. J. 46:577–583, 1997). So far, very few classes have been proved to be sandwich monotone, and the most famous of these are chordal graphs. Sandwich monotonicity of a graph class implies that minimal completions of arbitrary graphs into that class can be recognized and computed in polynomial time. For minimal completions into strongly chordal or chordal bipartite graphs no polynomial-time algorithm has been known. With our results such algorithms follow for both classes. In addition, from our results it follows that all strongly chordal graphs and all chordal bipartite graphs with edge constraints can be listed efficiently.     

Aversion to inequality in Italy and its determinants

The main goal of this paper is to estimate the preferences of the Italian society towards equity in order to verify whether preferences (i) have changed across the years, and (ii) can be related to specific socio-demographic characteristics. Introducing equity concerns in the implementation of economic policies is a fundamental problem faced by both economists and policy makers. This paper uses a social welfare function à la Jorgenson and Slesnick to estimate society’s aversion towards inequality by implementing a voting scheme for compiling individuals’ equity preferences into a social choice by majority rule. The results show that preferences are highly polarized toward a low and a high concern for equity aversion and that this concern is significantly related with several sociodemographic characteristics. Among them, income plays an important role with richer people tending to favor less equity. Results also show that preferences towards equity have changed across the years.