Model-based clustering of multivariate ordinal data relying on a stochastic binary search algorithm

We design a probability distribution for ordinal data by modeling the process generating data, which is assumed to rely only on order comparisons between categories. Contrariwise, most competitors often either forget the order information or add a non-existent distance information. The data generating process is assumed, from optimality arguments, to be a stochastic binary search algorithm in a sorted table. The resulting distribution is natively governed by two meaningful parameters (position and precision) and has very appealing properties: decrease around the mode, shape tuning from uniformity to a Dirac, identifiability. Moreover, it is easily estimated by an EM algorithm since the path in the stochastic binary search algorithm can be considered as missing values. Using then the classical latent class assumption, the previous univariate ordinal model is straightforwardly extended to model-based clustering for multivariate ordinal data. Parameters of this mixture model are estimated by an AECM algorithm. Both simulated and real data sets illustrate the great potential of this model by its ability to parsimoniously identify particularly relevant clusters which were unsuspected by some traditional competitors.     

Monopolistic Competition: Beyond the Constant Elasticity of Substitution

We propose a model of monopolistic competition with additive preferences and variable marginal costs. Using the concept of “relative love for variety,” we provide a full characterization of the free‐entry equilibrium. When the relative love for variety increases with individual consumption, the market generates pro‐competitive effects. When it decreases, the market mimics anti‐competitive behavior. The constant elasticity of substitution is the only case in which all competitive effects are washed out. We also show that our results hold true when the economy involves several sectors, firms are heterogeneous, and preferences are given by the quadratic utility and the translog.     

Multiple criteria decision analysis of treatment and land-filling technologies for waste incineration residues

In this paper, we present a real-world case realized in Switzerland on behalf of the federal agency in charge of the waste policy. The incineration of urban wastes generates hazardous residues that need specific treatment and/or land-filling technologies. The variety of local situations and appraisals led to the choice of very different solutions. Moreover, proponents were keen to propose new technologies. The purpose of this study was to provide the background for a national policy that would apply to all future projects.     

The impact of language and culture on perceived website usability

Online retailers offering their products across national and cultural borders are eager to enhance the usability of their websites to attract large numbers of visitors. The results of the present research show that the perceived usability increases when the website was originally conceived in the native language of the user. Thus, translation, even though of excellent quality, creates a cultural distance which impacts on the web users’ evaluation of the site. Conversely, where language is less important, such as in the evaluation of the quality of an offer, a consumer's native language has no impact on the buying decision.     

Mechanism Design with Collusion and Correlation

In a public good environment with positively correlated types, we characterize optimal mechanisms when agents have private information and can enter collusive agreements. First, we prove a weak‐collusion‐proof principle according to which there is no restriction for the principal in offering weak‐collusion‐proof mechanisms. Second, with this principle, we characterize the set of allocations that satisfy individual and coalitional incentive constraints. The optimal weakly collusion‐proof mechanism calls for distortions away from first‐best efficiency obtained without collusion. Allowing collusion restores continuity between the correlated and the uncorrelated environments. When the correlation becomes almost perfect, first‐best efficiency is approached. Finally, the optimal collusion‐proof mechanism is strongly ratifiable.     

Voluntas Symposium: Comments on Salamon and Sokolowski’s Re-conceptualization of the Third Sector

With their “Beyond Nonprofits: Re-conceptualizing the Third Sector”, Salamon and Sokolowski have made an important contribution to the ongoing debate on how to define the third sector. This Voluntas symposium brings together the comments of five leading scholars both supportive and critical of the new definition. The comments are based on a debate held at the conference of the International Society for Third Sector Research, in Stockholm in 2016.