Computing price trends in sequential auctions

This paper compares various methods used for measuring price trends in sequential auctions and draws on index number theory. Data from wine auctions are used to show that different methods applied to the same data may lead to significantly différent conclusions. Moreover the same method can even lead to opposite results depending on the way pairs are selected within the set of similar objects sold sequentially. Finally, the number of identical objects being sold also influences the price trend.Sequential auctions, Price aggregation, Price indices

Verifying Privacy-Type Properties in a Modular Way

Formal methods have proved their usefulness for analysing the security of protocols. In this setting, privacy-type security properties (e.g. vote-privacy, anonymity, unlink ability) that play an important role in many modern applications are formalised using a notion of equivalence. In this paper, we study the notion of trace equivalence and we show how to establish such an equivalence relation in a modular way. It is well-known that composition works well when the processes do not share secrets. However, there is no result allowing us to compose processes that rely on some shared secrets such as long term keys. We show that composition works even when the processes share secrets provided that they satisfy some reasonable conditions. Our composition result allows us to prove various equivalence-based properties in a modular way, and works in a quite general setting. In particular, we consider arbitrary cryptographic primitives and processes that use non-trivial else branches. As an example, we consider the ICAO e-passport standard, and we show how the privacy guarantees of the whole application can be derived from the privacy guarantees of its sub-protocols

Composing security protocols: from confidentiality to privacy

Security protocols are used in many of our daily-life applications, and our privacy largely depends on their design. Formal verification techniques have proved their usefulness to analyse these protocols, but they become so complex that modular techniques have to be developed. We propose several results to safely compose security protocols. We consider arbitrary primitives modeled using an equational theory, and a rich process algebra close to the applied pi calculus. Relying on these composition results, we derive some security properties on a protocol from the security analysis performed on each of its sub-protocols individually. We consider parallel composition and the case of key-exchange protocols. Our results apply to deal with confidentiality but also privacy-type properties (e.g. anonymity) expressed using a notion of equivalence. We illustrate the usefulness of our composition results on protocols from the 3G phone application and electronic passport

Trace Equivalence Decision: Negative Tests and Non-determinism

We consider security properties of cryptographic protocols that can be modeled using the notion of trace equivalence. The notion of equivalence is crucial when specifying privacy-type properties, like anonymity, vote-privacy, and unlinkability. In this paper, we give a calculus that is close to the applied pi calculus and that allows one to capture most existing protocols that rely on classical cryptographic primitives. First, we propose a symbolic semantics for our calculus relying on constraint systems to represent infinite sets of possible traces, and we reduce the decidability of trace equivalence to deciding a notion of symbolic equivalence between sets of constraint systems. Second, we develop an algorithm allowing us to decide whether two sets of constraint systems are in symbolic equivalence or not. Altogether, this yields the first decidability result of trace equivalence for a general class of processes that may involve else branches and/or private channels (for a bounded number of sessions)

In the context of researching local environmental changes, what do Ashevillian discourses on population growth and development tell us about their relationships and interactions with the environment?

The city of Asheville (North Carolina, USA) is facing increasing social and environmental pressures like many other popular destinations. They include population growth that is most noticed through the processes of gentrification and exurbanization (mountain-side-top building), with all of those linked to amenity migration. The social and economic dependency on the natural environment is clear, and yet how do people perceive the local environmental changes that are due to these pressures? The research question here is "In the context of researching local environmental changes, what do Ashevillian discourses on population growth and development tell us about their relationships and interactions with the environment?" The research was led to contribute to the PIAF project, "Programme Interdisciplinaire sur les indicateurs Autochtones de la Faune et de la flore", (ANR-13-JSH1-0005-01), and will later be used in comparisons with research sites in 3 other countries to try to see to what extent local biodiversity can serve as an indicator of wider environmental changes. Two and a half months were spent in Asheville to carry out the shared PIAF fieldwork methods. This resulted in a total of 45 semi-structured interviews and 20 free-lists with follow-up interviews, some participant observation as well as a full ethnographic immersion in the city life. The sample was constructed through a snow-ball method on-site without the aim of being representative. The first chapter exposes the way that the majority of respondents chose to speak of local changes through the lens of population growth and development, and how they associated these to tourism, house prices, traffic, half-backs and more. We found that the growth of the urban population is not just restricted to Asheville, but that the perceptions of the processes of gentrification and mountain-side development, for example, varied from one respondent to the other often because of how differently they had been personally affected by them. The second chapter focused on detailing the perception of the changes to the social and built environments, using the example of gentrification, as seen through the opinions expressed and the use of the land. We found that the arrival of different ideas brought conflicts that served to point out different relationships with the environment, namely between locals and new amenity migrants. The third chapter looks more precisely at how discourses on changes in local biodiversity show a one-directional representation of human-wildlife interactions. The examples of black bears, deer, raccoons and turkeys entering into Asheville illustrated, for the respondents, how development is perceived to encroach on wild habitat. What is at stake is to display the perceptions people have of local changes to their environment as they contribute significantly to their individual, and altogether collective, actions in the human-environment interactions. Local policies aimed at addressing population growth and pressure on resources benefit from understanding what is attracting people to the area, what is the range of values displayed by locals and newcomers. This helps to explain what may be causing conflicts or alliances between people and between people and their environment

La structuration de la pratique du covoiturage en France : jeu d'acteurs et institutionnalisation

En France, le covoiturage semble être né avec la création de l'association Allostop en 1958 qui, la première, a mis en place un « autostop organisé » ; le terme « covoiturage » ayant fait son apparition beaucoup plus tard, en 1989. A l'origine destinée à favoriser la mobilité de jeunes gens pas suffisamment fortunés pour s'offrir une voiture, la pratique a progressivement évolué pour davantage répondre aux enjeux de la congestion urbaine, du coût d'usage automobile et de la protection de l'environnement. Le covoiturage se trouvait alors en 2004 - année de la réalisation de ce terrain - réapproprié par une multitude d'acteurs aux statuts et objectifs diversifiés. Du fait de cette diversité, les centres de décision se trouvent difficiles à repérer. Il s'agira alors ici dans un premier temps de décrire les acteurs du covoiturage en essayant de déterminer leur statut et leurs fonctions dans la promotion de cette pratique. Dans un second temps, l'analyse détaillée des acteurs permettra de mettre en lumière le jeu d'acteurs autour du covoiturage en France afin d'en dégager les forces et les faiblesses et ainsi d'évaluer les conditions de développement de cette pratique à l'échelle organisationnelle.pratique du covoiturage ; France

An approach to the estimation of the distribution of marginal valuations from discrete choice data

Models such as the mixed logit are often used to measure the distribution of the marginal value of a good based on discrete choice panel data. There are however serious specification and identification issues that are rarely addressed. The consequences for results may be dramatic. This paper points out the issues and presents an approach to dealing with them that may be applied under some circumstances. The issues and the approach are illustrated using a dataset designed to measure the value of travel time.Discrete choice; valuation; mixed logit

Forecasting the Trade Flow of Denmark

This paper presents the modeling of a dynamic gravity equation in order to forecast the trade flows of goods in and out of Denmark, including transit goods. This analysis is part of a research project where the objective is to establish the future flow of goods for Denmark as well as the node points in order to be able to optimize public investments. The paper only focuses on the construction of the gravity equation that will be used for setting up scenarios for the future flow of goods from and to Denmark. We compare different methods of estimation of the gravity equation used in previous studies and propose a robust estimation of a dynamic gravity equation. Examples of the forecasting method are presented for illustration

Transport consumption inequalities and redistributive effects of taxes: A comparison of France, Denmark and Cyprus

We evaluate household transport consumption inequalities in France, Denmark and Cyprus, investigate their temporal dynamics and estimate the redistributive effects of taxes on different commodity categories. A comparative analysis is carried out in light of the differences between these countries, most notably in terms of car taxation systems and car ownership levels. A decomposition by expenditure component of the Gini index is applied, using household-level data from repeated cross-sections of expenditure surveys spanning long time periods. The results highlight the effect of car social diffusion. The relative contribution of vehicle use items to total expenditure inequality decreases over time, thus reflecting the more and more widespread use of the car. Moreover, fuel taxes become regressive (i.e. they affect the poor more than the rich), while the progressive character of taxes on the remaining car use commodities weakens with time. Taxes on transport goods and services as a whole are progressive (i.e. they affect the rich more than the poor). However, this is principally due to the progressivity of taxes on automobile purchases. The progressivity of taxes on car purchases is by far much stronger in Denmark. In this country, these taxes are so high that car purchase costs can be afforded only by high incomes. These findings underline the fact that equity issues should not be overlooked when designing policies to attenuate the environmental impact of cars. Increasing car use costs, notably fuel prices, through an increase of uniform taxes would be particularly inequitable.Inequality; transport consumption; household expenditure surveys; Gini index; decomposition by component; redistributive effects of taxes

The Declining Price Effect in Sequential Auctions: What Theory Does Not Predict

This paper studies different explanations given for the "price decline anomaly" in sequential auctions, a phenomenon also known as the "afternoon effect". It surveys the dedicated theoretical models and then explores the influence of the institutional or market characteristics (of the sale) on the price trend. Next , it presents different methods used for measuring price trends and analytically identifies the differences between them. Finally, data from wine auctions are used to show that different methods may lead to opposite trends from the same data and that the number of identical objects being sold influences the price trend.multiple unit auctions; price decline; index Numbers; bootstrap simulations