Do clubs foster provision success ?

We report the results of an experiment on the provision of a step-level collective good. We compare subjects’ behavior in a public good game and in a club good game. In the club good game, players who contribute less than the amount required to become a member, do not benefit from the collective good. Compared to the benchmark step-level public good, we find that the introduction of a small membership fee has surprisingly strong effects. It increases significantly the provision success of the collective good.

From Bound Duties to Actual Protection: Industrial Liberalisation in the Doha Round. ENEPRI Working Paper No. 41, 2005

In the background of the Doha Round of trade negotiations, this study proposes a CGE assessment of multilateral liberalisation of market access for non-agricultural products. The scenarios considered include the so-called ‘Girard proposal’ (with alternative choices for the coefficient involved), the removal of tariff peaks and complete liberalisation. This study is the first to take into account the difference between bound and applied tariffs, while considering all the enforced preferential trade arrangements and computing tariff cuts at the detailed product level (HS-6 classification). Although the liberalisation of market access for non-agricultural products is found to be welfare-enhancing at the world level, cross-country distributive effects prove significant. A soft liberalisation would not significantly reduce applied duties in developing countries, owing to their considerable binding overhang. By contrast, a deep liberalisation would entail fierce price competition among those developing countries that are largely specialised in similar sectors and in the same product quality range

Unsupervised and semi-supervised clustering with learnable cluster dependent kernels.

Despite the large number of existing clustering methods, clustering remains a challenging task especially when the structure of the data does not correspond to easily separable categories, and when clusters vary in size, density and shape. Existing kernel based approaches allow to adapt a specific similarity measure in order to make the problem easier. Although good results were obtained using the Gaussian kernel function, its performance depends on the selection of the scaling parameter. Moreover, since one global parameter is used for the entire data set, it may not be possible to find one optimal scaling parameter when there are large variations between the distributions of the different clusters in the feature space. One way to learn optimal scaling parameters is through an exhaustive search of one optimal scaling parameter for each cluster. However, this approach is not practical since it is computationally expensive especially when the data includes a large number of clusters and when the dynamic range of possible values of the scaling parameters is large. Moreover, it is not trivial to evaluate the resulting partition in order to select the optimal parameters. To overcome this limitation, we introduce two new fuzzy relational clustering techniques that learn cluster dependent Gaussian kernels. The first algorithm called clustering and Local Scale Learning algorithm (LSL) minimizes one objective function for both the optimal partition and for cluster dependent scaling parameters that reflect the intra-cluster characteristics of the data. The second algorithm, called Fuzzy clustering with Learnable Cluster dependent Kernels (FLeCK) learns the scaling parameters by optimizing both the intra-cluster and the inter-cluster dissimilarities. Consequently, the learned scale parameters reflect the relative density, size, and position of each cluster with respect to the other clusters. We also introduce semi-supervised versions of LSL and FLeCK. These algorithms generate a fuzzy partition of the data and learn the optimal kernel resolution of each cluster simultaneously. We show that the incorporation of a small set of constraints can guide the clustering process to better learn the scaling parameters and the fuzzy memberships in order to obtain a better partition of the data. In particular, we show that the partial supervision is even more useful on real high dimensional data sets where the algorithms are more susceptible to local minima. All of the proposed algorithms are optimized iteratively by dynamically updating the partition and the scaling parameter in each iteration. This makes these algorithms simple and fast. Moreover, our algorithms are formulated to work on relational data. This makes them applicable to data where objects cannot be represented by vectors or when clusters of similar objects cannot be represented efficiently by a single prototype. Our extensive experiments show that FLeCK and SS-FLeCK outperform existing algorithms. In particular, we show that when data include clusters with various inter-cluster and intra-cluster distances, learning cluster dependent kernel is crucial in obtaining a good partition

The Cost of non-Maghreb: Achieving the Gains from Economic Integration

The purpose of this paper is to estimate the impact of the integration of Maghreb countries into a free trade area on the main macroeconomic aggregates. By using the MIRAGE model and MacMap database, we tested different scenarios to estimate the gains or the potential losses of various plans of trade integration (Free trade area for the Maghreb countries, Custom Union between Maghreb countries, Maghreban Common Market). Our study suggests that the overall gains from liberalizing trade in goods (and removing various regulatory non-tariff barriers in the process) could reach at least USD 350 million. The increase in revenue through increases in production and wages would positively affect welfare levels for Maghreb consumers. The dynamic gains from liberalizing trade in goods can outstrip the static gains, with productivity improvements as the main driver. Our analysis shows that the creation of a common market is probably the most interesting and efficient option for the Maghreb countries.Free Trade Area, Maghreb, and CGE Model

Pour une utilisation durable des nappes d'eau souterraine : une approche par les incitations

La gestion d'une ressource en commun pose le problème de la surexploitation. Cette possibilité se produit lorsque l'appropriateur cherche à maximiser son profit tout en partageant le coût de son exploitation avec les autres appropriateurs. C'est le modèle de la tragédie des communs de Hardin (1968). Les solutions proposées pour dépasser ce dilemme sont la gestion centralisée de la ressource, l'instauration des droits de propriété transférable et la gestion collective. La Tunisie a opté pour ce dernier choix à travers une gestion décentralisée par les groupements à intérêt collectif (GIC). L'implémentation des règles dans une action collective articulée autour de l'exploitation d'une nappe à accès libre constitue la finalité du papier. Pour cela, nous nous proposons, dans le cadre de ce travail, la réalisation d'un diagnostic de la situation étudiée en vue de mieux appréhender son fonctionnement. Nous cherchons à effectuer une représentation sous forme de jeux du problème d'accès à la nappe et de l'allocation de la ressource, situations où se pose la question de l'implémentation des règles. La structure du Dilemme du Prisonnier est souvent utilisée pour rendre compte de l'exploitation de la ressource en commun. Nous nous gardons d'effectuer cette appréciation à priori tant qu'une observation se basant sur une méthodologie d'approche n'ait pas confirmé une structure particulière de jeu. La revue de la littérature a permis de distinguer d'autres jeux possibles permettant de rendre compte des problèmes dans une action collective. Afin d'identifier ces jeux, nous décomposerons les cas étudiés en autant d'actions possibles pertinentes. L'approche adoptée à cet effet s'inspirera de celle proposée par Ostrom : l'Institutional Analysis Developpement (IAD). Elle consiste dans la définition des variables suivantes : les acteurs participants, l'information dont ils disposent, leurs stratégies et leurs gains respectifs. Ce travail aura pour terrain d'étude la plaine de Kairouan

Nonpoint source pollution: An experimental investigation of the Average Pigouvian Tax

The “Average Pigouvian Tax” (APT) was proposed by Suter et al. (2008) to reduce the financial burden of the standard ambient tax. This instrument consists in a standard ambient tax divided by the number of firms, which requires polluters to cooperate in order to achieve the social optimum. To enable polluters to cooperate, communication is allowed. We introduce different types of communication: cheap talk, exogenous costly communication (communication is imposed), and endogenous costly communication (conducted on a voluntary basis after a vote). Our experiment confirms that the instrument induces polluters to reduce their emissions under cheap talk. However, we find that group emissions are less reduced when communication is costly. This result still holds even when we endogenize communication by introducing a voting phase

Le « paysage urbain » en question

L’article expose les orientations méthodologiques d’une recherche portant sur la notion de paysage urbain. La première partie précise les enjeux et les problématiques convoqués par cette notion – à travers notamment les débats actuels entre théoriciens et professionnels du paysage – et situe les champs de référence de cette recherche. La seconde partie présente les deux axes de recherche retenus. Le premier consiste en une approche généalogique de la construction artistique et conceptuelle du paysage urbain. Le deuxième s’inscrit dans une démarche sociologique à travers la réalisation d’une enquête qualitative dont l’article exposera les premières conclusions.The article presents methodological choices of a research about the notion of urban landscape. The first part outlines the issues and problems about this notion (especially through the current debates between landscape professionals and theorists) and make clear reference fields of the study. The second part presents two directions of research selected. First, a genealogical approach focuses on the artistic and conceptual construction of the urban landscape. The second axis is part of a sociological approach by carrying out a qualitative inquiry, which section outlines the first conclusions

Climate change effects on phytochemical compounds and antioxidant activity of Olea europaea L.

To tolerate water shortage and high temperature, olive cv. ‘Meski’, the main variety of table olives in Tunisia, developed several biochemical changes. The hereby study focused on the adaptation of the olive tree to the climatic conditions, considering the evaluation of phenolic compounds, chlorophylls, carotenoids, saponin and steroid synthesis, as well as the evaluation of the antioxidant activity. The analyses were made upon fresh leaves collected from three coastal areas of Tunisia (North (sub-humid), center (higher semi-arid) and South (lower arid)) and using different leaves’ extracts. The results emphasized that Southern ‘Meski’ trees had leaves with more polyphenols, flavonoids, o-diphenols and tannins compared with the Northern ones. From the North to the South, ‘Meski’ leaves showed an increase of carotenoids and a decrease of chlorophyll a and b contents. The highest level of antioxidant compounds of Southern leaves could be contributed to reduce the oxidative stress of the olive tree. The spectrophotometric analysis of the antioxidant capacity of leaves collected from central and Southern areas, based on DPPH and ABTS radical-scavenging activity, showed a higher value of antioxidant activity than the Northern ones, at different extract concentrations. Therefore, the increase of the analyzed bioactive compounds can be considered as a response of the tree to surround aggressions and to oppose the oxidative stress that results from the severity of climatic conditions, characteristic of the Southern area