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The general-to-specific (GETS) approach to modelling is widely employed in the modelling of economic series, but less so in financial volatility modelling due to computational complexity when many explanatory variables are involved. This study proposes a simple way of avoiding this problem and undertakes an out-of-sample forecast evaluation of the methodology applied to the modelling of weekly exchange rate volatility. Our findings suggest that GETS specifications are especially valuable in conditional forecasting, since the specification that employs actual values on the uncertain information performs particularly well.

Technological choices are multi-dimensional and thus one needs a multidimensional methodology to identify best available techniques. Moreover, in the presence of environmental externalities generated by productive activities, ?best? available techniques should be best from Society's point of view, not only in terms of private interests. In this paper we develop a comprehensive modeling tool, based on methodologies appropriate to serve these two purposes, namely linear programming and internalization of external costs. We conclude that in this context there is in general not a single best available technique (BAT), but well a best combination of available techniques to be used (BCAT). We take a fictitious but plausible numerical example in the lime industry. For a hypothetical plant that has to meet a given demand, we build an original technical economic model within which two scenarios are considered: minimizing the private costs and minimizing the generalized costs (private costs plus external costs). In the first case, only the cheapest fuel is used in all kilns. But in the second case, where the environmental external costs are included, fuel switches occur and cleaner techniques are used. Extending the analysis to the choice of kilns, we find that the socially best combination of available techniques (S-BCAT) is not a fixed one : it varies as a function of the external costs. We therefore trace in a single diagram the whole profile of these best techniques as successive solutions of our linear programs. We conclude by stressing that external cost internalization does influence not only the choice of techniques, but also their appropriate use. Moreover, local environmental conditions play a major role in that choice and in determining that use.

The paper considers a model of a federation with two heterogeneous regions that try to attract the capital by competing in capital income taxes and public investment that enhance the productivity of capital. The regions' choices determine the allocation of capital across the regions and their revenues under a tax sharing scheme. This framework allows for the examination of different approaches to fiscal equalization schemes (Boadway and Flatters, 1982, and Weingast, 2006). We show that tax competition distorts (downwards) public investments and that the equalization grants discourage public investments with a little effect on equilibrium taxes. However, the equalization schemes remain beneficial for the federation and, provided that the degree of asymmetry is small, for each region as well.

In essence, any international environmental agreement (IEA) implies cooperation of a form or another. The paper seeks for logical foundations of this. It first deals with how the need for cooperation derives from the public good aspect of the externalities involved, as well as with where the source of cooperation lies in cooperative game theory. In either case, the quest for efficiency is claimed to be at the root of cooperation. Next, cooperation is considered from the point of view of stability. After recalling the two competing concepts of stability in use in the IEA literature, new insights on the nature of the gamma core in general are given as well as of the Chander-Tulkens solution within the gamma core. Free riding is also evaluated in relation with the alternative forms of stability under scrutiny. Finally, it is asked whether with the often mentioned virtue of "self enforcement" any conceptual gain is achieved, different from what is meant by efficiency and stability. A skeptical answer is offered, as a reply to Barrett's (2003) attempt at giving the notion a specific content.

In this paper, we study a pure exchange economy with idiosyncratic uncertainty, hidden action and multiple consumption goods. We consider two different market structures: contingent markets on the one hand, and financial and spot markets on the other hand. We propose a competitive equilibrium concept for each market structure. We show that the equilibrium with contin- gent markets is efficient in an appropriate sense, while the equilibrium with financial and spot markets is inefficient, provided that assumptions on preferences more general than those usually considered in the literature hold.

In this chapter written for a forthcoming Handbook of Financial Time Series to be published by Springer-Verlag, we review the econometric literature on dynamic duration and intensity processes applied to high frequency financial data, which was boosted by the work of Engle and Russell (1997) on autoregressive duration models.

Tradable permits are now widely used to control pollution. We investigate the implications of setting up such a system in another area population control, either domestically or at the global level. We first generalize the framework with both tradable procreation allowances and tradable procreation exemptions, in order to tackle both over- and under-population problems. The implications of procreation rights for income inequality and education are contrasted. We decompose the scheme's impact on redistribution into three effects, one of them, the tradability effect, entails the following: with procreation exemptions or expensive enough procreation allowances, redistribution benefits the poor. In contrast, cheap procreation allowances redistribute resources to the rich. As far as human capital is concerned, natalist policy worsens the average education level of the next generation, while population control enhances it. If procreation rights are granted to countries in proportion to existing fertility levels (grandfathering) instead of being allocated equally, population control can be made even more redistributive. Our exploratory analysis suggests that procreation entitlements offer a promising tool to control population without necessarily leading to problematic distributive impact, especially at the global level.

A free entry model with linear costs is considered where firms first choose their entry time and then compete in the market according to the resulting timing decisions. Multiple equilibria arise allowing for infinitely many industry output configurations encompassing one limit-output dominant firm and the Cournot equilibrium with free entry as extreme cases. Sequential entry is never observed. Both Stackelberg and Cournot-like outcomes are sustainable as equilibria however. When the number of incumbents is given, entry is always prevented, and industry output is sometimes larger than the entry preventing level.

Empirical testing of asymmetric information in the insurance market has uncovered a negative correlation between risk levels and insurance purchases, rather than the positive correlation predicted by the standard insurance theory. Hemenway (1990) proposes an explanation for this negative correlation, called "propitious selection". He argues that potential insurance buyers have different tastes for risk and that "individuals who are highly risk avoiding are more likely both to try to reduce the hazard and to purchase insurance" (p. 1064). Chiappori and Salanié (2000) also suggest that this line of argument, which they call "cherry picking", may explain the observed negative correlation. In this paper, we show that the propitious selection argument does not imply negative correlation between risk levels and insurance purchases, because it fails to take into account the supply side of the insurance market. To illustrate this claim, we provide a model where, although we assume that individuals differ in risk aversion and that the more risk averse individuals exert more precaution and buy more insurance, we end up with a positive correlation between risk and insurance purchases at equilibrium. The reason is that, in any separating equilibrium, the more risk averse individuals face insurance overprovision which, combined with moral hazard, increases their risk relative to the less risk averse individuals. To obtain the negative correlation between risk and insurance purchases, one further needs the extra condition of decreasing marginal willingness to pay for the less risk averse individuals. Finally, we find that propitious selection has profound policy implications for social insurance.

The reduction theory of David F. Hendry provides a comprehensive probabilistic framework for the analysis and classification of the reductions associated with empirical econometric models. However, it is unable to provide an analysis on the same underlying probability space of the first reduction - and hence the subsequent reductions - given a commonplace theory of social reality, namely the joint hypotheses that the course of history is indeterministic, that history does not repeat itself, and that the future depends on the past. As a solution this essay proposes that the elements of the underlying outcome space in Hendry's theory are interpreted as indeterministic worlds made up of historically inherited particulars.

This paper investigates the effect of ethnolinguistic conflict on redistribution. The analysis focuses on the conflict arising between "peripheral" minority groups and a dominant "center". We propose an index of linguistic conflict that (i) encompasses both diversity and polarization, and (ii) accounts for the distance between languages. Our results suggest that linguistic diversity is a better predictor of redistribution than linguistic polarization. We also find that incorporating linguistic distances leads to better predictions.

In least squares, least absolute deviations, and even generalized M-estimation, outlying observations sometimes strongly influence the estimation result, masking an important and interesting relationship existing in the majority of observations. The S-estimators are a class of estimators that overcome this difficulty by smoothly downweighting outliers in fitting regression functions to data. In this paper, we propose a method of model selection suitable in S-estimation. The proposed method chooses a model to minimize a criterion named the penalized S-scale criterion (PSC), which is decreasing in the sample S-scale of fitted residuals and increasing in the number of parameters. We study the large sample behavior of the PSC in nonlinear regression with dependent, heterogeneous data, to establish sets of conditions sufficient for the PSC to consistently select the model with the best fitting performance in terms of the population S-scale, and the one with the minimum number of parameters if there are multiple best performers. Our analysis allows for partial unidentifiability, which is often a practically important possibility when selecting one among nonlinear regression models. We offer two examples to demonstrate how our large sample results could be applied in practice. We also conduct Monte Carlo simulations to verify that the PSC performs as our large sample theory indicates, and assess the reliability of the PSC method in comparison with the familiar Akaike and Schwarz information criteria.

We examine the relationship between contracting out and the wage elasticity of labor demand in outsourcing plants. A simple theoretical model suggests that firms engaged in contracting out have lower wage elasticities. Estimating plant level dynamic labor demand equations for Irish manufacturing we find evidence supportive of this.

The veil of ignorance has been used often as a tool of recommending what justice requires with respect to the distribution of wealth. We complete Harsanyi's model of the veil of ignorance by appending information permitting objective comparisons among persons. We show that the veil-of-ignorance conception of John Harsanyi, so completed, and Donald Dworkin's, when modeled formally, recommend wealth allocations in conflict with the prominently espoused view that priority should be given to the disabled in wealth allocation.

The formulation of the problem of justice among generations as the problem of finding an ordering of infinite utility streams is examined within the "social welfare functional" approach to social choice. This formulation usually presumes a double reduction, not only the classical "welfarist" reduction, according to which "utility" provides all the information required to construct a social evaluation rule, but also the aggregation of the individual utility levels at each generation into a single utility level. We shall argue that this second type of reduction obliterates the relationship between the values judgments made in the social evaluation ofthe welfare of the presently living generation with that of future generations and does not emphasize the capacity for many social evaluation criteria (including pure utilitarianism and Leximin) to "proliferate" from the present generation to any larger set of generations. Our results concerning the orderings generated by such proliferating rules are compared to characterisations already given in the literature.

In many applications it is possible to justify a reasonable bound for possible variation of subgradients of objective function rather than for their uniform magnitude. In this paper we develop a new class of efficient primal-dual subgradient schemes for such problem classes.

We consider a model of daily newspapers' competition to test the validity of the so called "theory of the circulation spiral". According to it, the interaction between the newspapers and the advertising markets drives the newspaper with the smaller readership into a vicious circle, finally leading it to death. In a model with two newspapers, we show that, contrary to this conjecture, the dynamics envisaged by the proposers of the theory, does not always lead to the elimination of one of them.

In general, analyses of voting power are performed through the notion of a simple voting game (SVG) in which every voter can choose between two options: 'yes' or 'no'. Felsenthal and Machover (1997) introduced the concept of ternary voting games (TVGs) which recognizes abstention alongside. They derive appropriate generalizations of the Shapley-Shubik and Banzhaf indices in TVGs. Braham and Steffen (2002) argued that the decision-making structure of a TVG may not be justified. They propose a sequential structure in which voters first decide between participation and abstention and then between yes or no. The purpose of this paper is twofold. First, it compares the two approaches and shows how the probabilistic interpretation of power provides a unifying characterization of analogues of the Banzhaf (Bz) measure. Second, using the probabilistic approach we shall prove a special case of Penrose's Limit Theorem (PLT). This theorem deals with an asymptotic property in weighted voting games with an increasing number of voters. It says that under certain conditions the ratio between the voting power of any two voters (according to various measures of voting power) approaches the ratio between their weights. We show that PLT holds in TVGs for analogues of Bz measures, irrespective of the particular nature of abstention.

Starting from the US Sky Trust claim that the "the sky belongs to us equally", this paper distinguishes two sources through which overlapping generations may consent to the use of the environment whom they are the owners: the common consent of all generations reached behind the Rawlsian veil of ignorance and the specific consents of generations born at different time periods. It proposes two institutions: a fund mandated to implement the common consent by auctioning permits to firms and a voting procedure to implement the specific consents by choosing each generation's preferred level of environmental maintenance. The analysis shows how the specific consent may be, each period, operative or inoperative and that there may be at most two switches between these two regimes on the transition path. Starting from the business as usual steady state, the introduction of these institutions always immediately increases the environmental quality, but the magnitude of this gain may be temporary and decrease if capital accumulation is strongly evicted by the policy. On the opposite, we stress a case in which the introduction of the policy has beneficial effects both on wealth and quality.

One important aspect of financial markets is that there might be some traders that intentionally mislead other market participants by creating illusions in order to obtain a profit. We call this new concept illusionary finance. We present an analysis of how illusions can be created and disseminated in financial markets based on certain psychological principles that explain agents' decisions under time pressure and polysemous signals. We develop a simple model that incorporates the illusions in the price formation process. Furthermore, using powerful simulations, we show how illusions can be incorporated, directly or indirectly, in the expected prices of the traders.

We analyze the welfare consequences of an increase in the commissions charged by intermediaries in auction markets. We argue that while commissions are similar to taxes imposed on buyers and sellers the question of incidence deserves a new treatment in auction markets. We show that an increase in commissions makes sellers worse off, but buyers may strictly gain. The results are therefore strikingly different from the standard result that all consumers weakly lose after a tax or a commission increase. Our results are useful for evaluating compensation in price fixing conspiracies; in particular they suggest that the method used to distribute compensations in the class action against auction houses Christie's and Sotheby' was misguided.

We present a model of generation and network investment in a competitive electricity system. The model focuses on the duality of long-and short-term locational signals introduced in the European Regulation 1228/2003 for enhancing cross border trade of electricity among Member States. The model assumes that the market consists of spot and transmission submarkets. Generators, consumers and a TSO operate on that market; none of these agents has market power. Lumpiness of investments is one of the problems that may render generation and network adequacy difficult to achieve. We take up this question and apply some formalism formerly developed by O'Neill and co-authors for the unit commitment problem in order to construct multipart tariffs that insure the adequate development of the resources both in generation and the grid. In the process, we recover the standard nodal pricing as part of that multipart tariff. We address the questions of cost reflectiveness and non discrimination imposed by Regulation 1228/2003.

This paper analyzes the properties of three capacity games in an oligopolistic market with Cournot players. In the first game, capacity and the operation of that capacity is determined simultaneously. This is the classic open-loop Cournot game. In the second game capacity is decided in the first stage and the operation of that capacity is determined in the second stage. The first stage decision of each player is contingent on the solution of the second-stage game. This is a two-stage, closed-loop game. We show that when the solution exists, it is the same as the solution in the first game. However, it does not always exist. The third game has three stages with a futures position taken between the capacity stage and the operations stage and is also a closed-loop game. As with the second game, the equilibrium is the same as the open-loop game when it exists. However, the conditions for existence are more restrictive once a futures market is added. When both games have an equilibrium, the solution values are identical. The results are very different from games with no capacity stage as studied by Allaz and Vila (1993), which have been used to argue that futures markets can ameliorate market power.

In applying the common agency framework to the context of an oligopolistic industry, we want to go beyond the classical dichotomy between Cournot and Bertrand competition. We define two games, the oligopolistic game and the corresponding concept of oligopolistic equilibrium, and an associated auxiliary game that can be interpreted as a common agency game and that has the same set of equilibria. The parameterization of the set of (potential) equilibria in terms of competitive toughness is derived from the first order conditions of this auxiliary game. The enforceability of monopolistic competition, of price and quantity competition, and of collusion is examined in this framework. We then describe the (reduced) set of equilibria one would obtain, first in the nonintrinsic case and then in the case where a global approach would be adopted instead of partial equilibrium approach. Finally, we illustrate the use of the concept of oligopolistic equilibrium and of the corresponding parameterization by referring to the standard case of symmetric quadratic utility.

This paper explores the interplay between commodities' transportation costs and workers' commuting costs within a general equilibrium framework A la Dixit-Stiglitz. Workers are mobile and choose a region where to work as well as an intraurban location where to live. We show that a more integrated economy need not be more agglomerated. Instead, low transportation costs lead to the dispersion of economic activities. This is because workers are able to alleviate the burden of urban costs by being dispersed, while retaining a good access to all varieties. By contrast, low commuting costs foster the agglomeration of economic activities.

We put forward the Bond-Equity Yield Ratio (BEYR) as a criterium to dynamically allocate capital between equities and bonds on a short-term basis. Relying upon 30 years of monthly data for a large collection of countries, we use the cointegration, regimeswitching and ARMA-GARCH type methodologies to model and forecast the BEYR. While no model systematically beats the random walk from a statistical point of view, the out-of-sample forecasts show that the regime-switching model based on the forecasted probability generates the best and most consistent trading performance. A strategy based on the distribution percentiles is also consistent in its ability to outperform the buy-andhold strategies. All in all, the BEYR is a remarkable relative market pricing tool in the US as it delivers higher risk-adjusted returns than the equity yield on a short-term basis.

We discuss the welfare effects of bundling two products offered by two symmetric firms. We first show that, in terms of welfare, a monopoly does better than a duopoly in which each firm sell its good and that a monopoly selling the bundle does better than if it sells the bundle and the two goods separately. We also show that the choice of the mechanism for sharing the profits, obtained from the sales of the bundle, might have dramatic positive or negative effects even when the various optional mechanisms yield equal splits. In particular, the use of the Shapley value yields the highest total and consumer surpluses and the lowest producer surplus, while the weighted Shapley value totally reverses the outcome and yields profits which are very close (over 99 pourcent) to the full monopoly profits. Hence, as in the case of bundling by a monopolist, when competitors bundle they assist each other in deterring entry. However, in addition when competitors bundle, they can implicitly cooperate via the setting of the profit sharing rule and increase their profits at the expense of customers. This issue calls for some further attention by regulators.

In this paper we model an overlapping generations economy in which individuals are endowed with a renewable resource. This resource can be exploited at no cost by the young households and provided to production. A joy-of-giving bequest motive motivates the transfer of the unexploited resource to the heirs. The study of intertemporal equilibrium reveals three puzzles neglected by the literature on sustainability. First, the existence of a bequest motive does not automatically guarantee a sustainable future. Second, human exploitation may preserve the resource in equilibrium but at a sub-optimal rate; in this case, both those who exploit too much and those who do not exploit enough should run a capital stock lower than the golden rule level. Third, there exist fluctuating transitions to a sustainable future in which some generations are worse off than both their ascendants and their descendants.

This paper introduces and investigates the concept of repetitive risk aversion. The risk aversion of an increasing and concave utility function is repetitive if the fear of ruin, which measures agent's aversion to risking his entire income, is also increasing and concave. This is shown to be equivalent to the behaviorally meaningful condition that the risk premium is increasing at a non-increasing rate with the size of the bet. We find an additional justification for mixed risk aversion, which is known to be stronger than standard (and thus proper) risk aversion, in terms of this concept. We discuss several economic applications of repetitive risk aversion.

The transition from economic stagnation to sustained growth is often modelled thanks to "population-induced" productivity improvements, which are assumed rather than derived from primary assumptions. In this paper the effect of population on productivity is derived from optimal behavior. More precisely, both the number and location of education facilities are chosen optimally by municipalities. Individuals determine their education investment depending on the distance to the nearest school, and also on technical progress and longevity. In this setting, higher population density enables the set-up costs of additional schools to be covered, opening the possibility to reach higher educational levels. Using counterfactual experiments we find that one third of the rise in literacy can be directly attributed to the effect of density, while one sixth is linked to higher longevity and one half to technical progress. Moreover, the effect of population density in the model is consistent with the available evidence for England, where it is shown that schools were established at a high rate over the period 1540-1620.

In this paper we present a model of credit market with several homogeneous lenders competing to finance an investment project. Contracts are non-exclusive, hence the borrower can accept whatever subset of the offered loans. We use the model to discuss efficiency issues in competitive economies with asymmetric information and non-exclusive agreements. We characterize the equilibria of this common agency game with moral hazard and show that they all belong to the constrained Pareto frontier.

In recent decades, the concept of subjective probability has been increasingly applied to an adversary's choices in strategic games. A careful examination reveals that the standard construction of subjective probabilities does not apply in this context. We show how the difficulty may be overcome by means of a different construction, and provide an axiomatic foundation for it.

The idea of family altruism is that parents care only about their children's income and not about the use of this income made by the children. First, we establish dynamical properties which place the OLG model with family altruism halfway between the model with pure life-cyclers (Diamond (1965)) and the one with dynastic altruism (Barro (1974)). Then, we show that this concept leads to interesting fiscal policy conclusions less clear-cut and more realistic than those obtained with the two previous standard OLG models: a pay as you go social security is neutral but not a public debt.

In this note we consider a society that partitions itself into disjoint jurisdictions, each choosing a location of its public project and a taxation scheme to finance it. The set of public project is multi-dimensional, and their costs could vary from jurisdiction to jurisdiction. We impose two principles, egalitarianism, that requires the equalization of the total cost for all agents in the same jurisdiction, and efficiency, that implies the minimization of the aggregate total cost within jurisdiction. We show that these two principles always yield a core-stable partition but a Nash stable partition may fail to exist.

Recent contributions to microstructure theory hint at commonalities in the price-depth pairs which constitute the open limit order book. In this paper we provide empirical evidence that indeed a small number of latent factors, two for each side of the book, capture most of the variation in the price-depth pairs. The results also indicate that a heterogenous trader population is active on the buy and sell sides. The respective latent factors explaining the buy and sell side variation exhibit specific dynamics. When we exploit results from microstructure theory to empirically assess whether the majority of the book variation is due to either informational effects or non-informational fluctuations of liquidity we obtain mixed results.

In the Dixit-Stiglitz model of monopolistic competition, entry of firms is socially too small. Other authors have shown that excess entry is also a possibility with other preferences for diversity. We show that the cost structure and workers's rents can also explain excess entry.

Using a detailed sample made up of more than 20,000 investment rounds, we analyze the time to 'IPO', 'trade sale' and 'liquidation' for about 6,000 venture backed firms. We model these exit times using competing risks models. Biotech and internet firms have the fastest IPO exits. Internet firms are also the fastest to liquidate, while biotech firms are however the slowest. The conditional probability for IPOs are clearly non-monotonous with respect to time. As time flows, venture capital-backed firms first exhibit an increased likelihood of exiting to an IPO. However, after having reached a plateau, investments that have not yet exited have fewer and fewer possibilities of IPO exits as time increases. The bubble period from 1998 to 2000 was an 'easy money' period where venture capitalists gave much more money to firms, many of which did not offer outstanding growth potential as they tended to liquidate much faster than in normal times.

In this paper we consider mixed oligopoly markets for differentiated goods where private and public firms compete either in prices or quantities. We then study the welfare effect of privatization interpreted as partial strategic delegation of the public firm to a private manager with profit concern. It is shown that partial privatization improves welfare with quantity competition when goods are substitutes, and with price competition when goods are complements. However full privatization (complete delegation to private manager) can never be optimal. It is also shown that the public firm can make more profit than the private firm in equilibrium, and that this possibility is more likely under quantity competition. Turning to market regulation policy, we find: (i) that public and private firms should be taxed the same; and (ii) that price regulation is better than quantity regulation.

The theory of games against nature relies on complete preferences among all conceivable acts, i.e. among all potential assignments of consequences to states of nature (case 1). Yet most decision problems call for choosing an element from a limited set of acts. And in games of strategy, the set of strategies available to a player is given and not amenable to artificial extensions. In "Assessing Strategic Risk" (CORE DP 2005/20), R.J Aumann and J.H. Dreze extend the basic result of decision theory (maximisation of subjectively expected utility) to situations where preferences are defined only for a given set of acts, and for lotteries among these and sure consequences (case 2). In this paper, we provide a similar extension for two other situations: those where only the set of optimal elements from a given set of acts is known (case 3); and those where only a single optimal act is known (case 4). To these four cases correspond four nested sets of admissible subjective probabilities over the states or the opponent's strategies, namely a singleton in case 1 and increasing sets in cases 2-4. The results for cases 3 and 4 also define the extent to which subjective probabilities must be specified in order to solve a given decision problem or play a given game.

We estimate by Bayesian inference the mixed conditional heteroskedasticity model of (Haas, Mittnik, and Paolella 2004a). We construct a Gibbs sampler algorithm to compute posterior and predictive densities. The number of mixture components is selected by the marginal likelihood criterion. We apply the model to the SP500 daily returns.

Media industries are important drivers of popular culture. A large fraction of leisure time is devoted to radio, magazines, newspapers, the Internet, and television (the illustrative example henceforth). Most advertising expenditures are incurred for these media. They are also mainly supported by advertising revenue. Early work stressed possible market failures in program duplication and catering to the Lowest Common Denominator, indicating lack of cultural diversity and quality. The business model for most media industries is underscored by advertisers' demand to reach prospective customers. This business model has important implications for performance in the market since viewer sovereignty is indirect. Viewers are attracted by programming, though they dislike the ads it carries, and advertisers want viewers as potential consumers. The two sides are coordinated by broadcasters (or "platforms") that choose ad levels and program types, and advertising finances the programming. Competition for viewers of the demographics most desired by advertisers implies that programming choices will be biased towards the tastes of those with such demographics. The ability to use subscription pricing may help improve performance by catering to the tastes of those otherwise under-represented, though higher full prices tend to favor broadcasters at the expense of viewers and advertisers. If advertising demand is weak, program equilibrium program selection may be too extreme as broadcasters strive to avoid ruinous subscription price competition, but strong advertising demand may lead to strong competition for viewers and hence minumum differentiation ("la pens©♭e unique"). Markets (such as newspapers) with a high proportion of ad-lovers may be served only by monopoly due to a circulation spiral: advertisers want to place ads in the paper with most readers, but readers want to buy the paper with more ads.

We study a problem in a procurement setting in which an Original Equipment Manufacturer (OEM) wants to procure a set of items from a set of suppliers. Each supplier incurs a cost for supplying any subset/bundle of items, and each supplier's cost information is known only to him. The goal is to determine (i) an efficient allocation of suppliers to items and (ii) appropriate payments for suppliers. We formulate the problem of determining which supplier should supply what items as an integer program. We develop a method, which is based on the ellipsoid method, that solves the dual of the linear relaxation of the problem in polynomial time. We also show that the linear relaxation has an integral optimal solution.

In this paper we consider the scheduling problem of minimizing the sum of the weights of the late jobs on a single machine (1|rj| [sum] wj Uj ). A branch-and-check algorithm is proposed, where a relaxed integer programming formulation is solved by branch-and-bound and infeasible solutions are cut off using unfeasibility cuts. We suggest two ways to generate cuts. First we show how the algorithm by Carlier [7] can be modified to produce tightened "no-good" cuts. We then demonstrate how to create cuts by using constraint propagation. The branch-and check algorithm proposed is implemented in the Mosel modelling and optimization language. Computational experiments show that our algorithm outperforms the exact approach of P©♭ridy et al. [22], which, to our knowledge, is the best reported in the literature.

This paper sheds new light on the mixture of distribution hypothesis by means of a study of the weekly exchange rate volatility of the Norwegian krone. In line with other studies we find that the impact of information arrival on exchange rate volatility is positive and statistically significant, and that the hypothesis that an increase in the number of traders reduces exchange rate volatility is not supported. The novelties of our study consist in documenting that the positive impact of information arrival on volatility is relatively stable across three different exchange rate regimes, and in that the impact is relatively similar for both weekly volatility and weekly realised volatility. It is not given that the former should be the case since exchange rate stabilisation was actively pursued by the central bank in parts of the study period. We also report a case in which undesirable residual properties attained within traditional frameworks are easily removed by applying the log-transformation on volatilities.

We extend Krugman's (1980) two-country two-sector model to a setup with arbitrary numbers of countries and sectors. The extended model predicts an adequately defined "home market effect" only after controlling for cross-country differential accessibility through a theory-based linear filter. We bring that prediction to data by running a battery of non-parametric sign- and rank-tests that are closely related to those used in factor proportions theory. When applied to production and trade data on a cross-section of OECD and non-OECD countries, we find support for the presence of "home market effects" in a broad number of industries.

Two incumbent parties choose their platforms in a unidimensional policy space while facing a credible threat of an entry by the third party. Relative electoral support is the predominant objective of each party, and the third party enters only if it can displace one of the incumbents. In an equilibrium the two incumbents choose to prevent the entry and achieve the balance of power, i.e., splitting the electorate equally. The incumbents' positions might diverge more as compared to a system in which the parties seek to solely maximize the voters' support. Therefore, rank preoccupation under the threat of entry might contribute to more polarized political platforms of the two leading parties.

The purpose of this paper is to test econometrically the existence of fiscal interactions between Belgian municipalities. At the time of writing, the motivation was to provide scientific support to the lively debate on fiscal competition that took place among Belgian politicians in the late nineties. Two types of taxes are considered, for which Belgian municipalities have the decision power as to rates: the 'centimes additionnels' on the personal income tax and the 'pr©♭compte immobilier' which is a property tax. A dynamic adjustment model is specified and estimated using panel data for 598 municipalities over 15 years. The empirical results obtained bear upon two main points: (i) Some interaction definitely has prevailed between the municipalities' fiscal choices made during the observation period, for both taxes; (ii) However, the adjustment reactions to the other municipalities' fiscal choices have occurred over time at the very low yearly pace of 6% and 10%, respectively, of the discrepancy between the actual rates and the preferred rates.

We consider a two-country model of wage determination with private information in unionized imperfectlycomp etitive industries. We investigate the effects of separated product markets opening up for competition as well as of further market integration on the negotiated wage and the maximum delayin reaching an agreement. From an initial situation of reciprocal intra-industrytrade, an increase in product market integration will decrease the maximal delayin reaching an agreement. However, markets opening up for competition have an ambiguous effect on both the wage outcome and the maximum real delaytime in reaching an agreement.

Ascending price auctions typically involve a single price path with buyers paying their final bid price. Using this traditional definition, no ascending price auction can achieve the Vickrey-Clarke-Groves (VCG) outcome for general private valuations in the combinatorial auction setting. We relax this definition by allowing discounts to buyers from the final price of the auction (or alternatively, calculating the discounts dynamically during the auction) while still maintaining a single price path. Using a notion called universal competitive equilibrium prices, shown to be necessary and sufficient to achieve the VCG outcome using ascending price auctions, we define a broad class of ascending price combinatorial auctions in which truthful bidding by buyers is an ex post Nash equilibrium. Any auction in this class achieves the VCG outcome and ex post efficiency for general valuations. We define two specific auctions in this class by generalizing two known auctions in the literature [11, 24].

In this paper, we investigate the role of young adult mortality on child labor and educational decisions. We show that, in the absence of appropriate insurance mechanisms, the level of child labor is inefficient. It may be too high if parents are not very altruistic and anticipate positive transfers from their children in the future, but it can also be too low, in particular when parents expect to make positive transfers to their children in the future. Imperfect capital markets unambiguously increase the equilibrium level of child labor. We also show that a cash transfer conditional on child's schooling can always restore efficiency regarding child labor.