Search

This paper studies a spatial competition game between two firms that sell a homogeneous good at some pre-determined fixed price. A population of consumers is spread out over the real line, and the two firms simultaneously choose location in this same space. When buying from one of the firms, consumers incur the fixed price plus some transportation costs, which are increasing with their distance to the firm. Under the assumption that each consumer is ready to buy one unit of the good whatever the locations of the firms, firms converge to the median location: there is "minimal differentiation". In this article, we relax this assumption and assume that there is an upper limit to the distance a consumer is ready to cover to buy the good. We show that the game always has at least one Nash equilibrium in pure strategy. Under this more general assumption, the "minimal differentiation principle" no longer holds in general. At equilibrium, firms choose "minimal", "intermediate" or "full" differentiation, depending on this critical distance a consumer is ready to cover and on the shape of the distribution of consumers' locations.

International audience

During human evolution, individuals interacted mostly within small groups that were connected by limited migration and sometimes by conflicts. Which preferences, if any, will prevail in such scenarios? Building on population biology models of spatially structured populations, and assuming individuals’ preferences to be their private information, we characterize those preferences that, once established, cannot be displaced by alternative preferences. We represent such uninvadable preferences in terms of fitness and in terms of material payoffs. At the fitness level, individuals can be regarded to act as if driven by a mix of self-interest and a Kantian motive that evaluates own behavior in the light of the consequences for own fitness if others adopted this behavior. This Kantian motive is borne out from (genetic or cultural) kin selection. At the material-payoff level, individuals act as if driven in part by self-interest and a Kantian motive (in terms of material payoffs), but also in part by other-regarding preferences towards other group members. This latter motive is borne out of group resource constraints and the risk of conflict with other groups. We show how group size, the migration rate, the risk of group conflicts, and cultural loyalty shape the relative strengths of these motives.JEL codesA12, A13, B52, C73, D01, D63, D64, D91.

International audience; Crumbling social institutions, disintegrating structures, and a profound sense of uncertainty are the signs of our time. In this book, this contemporary crisis is explored and illuminated, providing narratives that suggest how the notion of hope can be leveraged to create powerful methods of organizing for the future. Chapters first consider theoretical and philosophical perspectives on hopeful organizing, followed by both empirical discussions about achieving change and more imaginative narratives of alternative and utopian futures, including an exploration of the differing roles of work, creativity, idealism, inclusivity and activism.

International audience; According to thinkers such as Zygmunt Bauman (2017a) and Wolfgang Streeck (2016), the current social world is ruled by a crumbling, morbidsystem. Old social institutions are failing and no new ones have yet emerged. This state in between ruling institutions has been labeled theinterregnum by Bauman (2012), using Antonio Gramsci’s metaphor. “The crisis consists precisely in the fact that the old is dying and the new cannot be born; in this interregnum a great variety of morbid symptoms appear” (Gramsci, 1971, p. 276), Gramsci foretold. Rather than literally denoting an era after the death of one sovereign yet before the enthronement of a new monarch, in today’s late global capitalism an interregnum denotes “times of uncertainty, and while [it is] raising many questions, three of them seem particularly pertinent to address at a time when rulers no longer can rule and the ruled no longer wish to be ruled: institutional disparity, the future of migrants and the endurability of the planet” (Bauman, 2012, p. 51). [...]

International audience; What kind of preferences should one expect evolution to favor? We propose a definition of evolutionary stability of preferences in interactions in groups of arbitrary finite size. Groups are formed under random matching that may be assortative. Individuals' preferences are their private information. The set of potential preferences are all those that can be represented by continuous functions. We show that a certain class of such preferences, that combine self-interest with morality of a Kantian flavor, are evolutionarily stable, and that preferences resulting in other behaviors are evolutionarily unstable. We also establish a connection between evolutionary stability of preferences and a generalized version of Maynard Smith's and Price's (1973) notion of evolutionary stability of strategies.

International audience; Does altruism and morality lead to socially better outcomes in strategic interactions than selfishness? We shed some light on this complex and non-trivial issue by examining a few canonical strategic interactions played by egoists, altruists and moralists. By altruists, we mean people who do not only care about their own material payoffs but also about those to others, and, by a moralist, we mean someone who cares about own material payoff and also about what would be his or her material payoff if others were to act like himself or herself. It turns out that both altruism and morality may improve or worsen equilibrium outcomes, depending on the nature of the game. Not surprisingly, both altruism and morality improve the outcomes in standard public goods games. In infinitely repeated games, however, both altruism and morality may diminish the prospects of cooperation, and to different degrees. In coordination games, morality can eliminate socially inefficient equilibria while altruism cannot.

This research received financial support from the Knut and Alice Wallenberg Research Foundation. Ingela Alger is grateful to ANR, Carleton University, and SSHRC for financial support and to the Stockholm School of Economics for its hospitality.; International audience; What preferences will prevail in a society of rational individuals when preference evolution is driven by the resulting payoffs? We show that when individuals’ preferences are their private information, a convex combination of selfishness and morality stands out as evolutionarily stable. We call individuals with such preferences homo moralis. At one end of the spectrum is homo oeconomicus, who acts so as to maximize his or her own payoff. At the opposite end is homo kantiensis, who does what would be “the right thing to do,” in terms of payoffs, if all others would do likewise. We show that the stable degree of morality—the weight placed on the moral goal—is determined by the degree of assortativity in the process whereby individuals are matched to interact.

International audience; According to Hamilton's (1964a, b) rule, a costly action will be undertaken if its fitness cost to the actor falls short of the discounted benefit to the recipient, where the discount factor is Wright's index of relatedness between the two. We propose a generalization of this rule, and show that if evolution operates at the level of behavior rules, rather than directly at the level of actions, evolution will select behavior rules that induce a degree of cooperation that may differ from that predicted by Hamilton's rule as applied to actions. In social dilemmas there will be less (more) cooperation than under Hamilton's rule if the actions are strategic substitutes (complements). Our approach is based on natural selection, defined in terms of personal (direct) fitness, and applies to a wide range of pairwise interactions.

We analyze how family ties affect incentives, with focus on the strategic interaction between two mutually altruistic siblings. The siblings exert effort to produce output under uncertainty, and they may transfer output to each other. With equally altruistic siblings, their equilibrium effort is nonmonotonic in the common degree of altruism, and it depends on the harshness of the environment. We define a notion of local evolutionary stability of degrees of sibling altruism and show that this degree is lower than the kinship-relatedness factor. Numerical simulations show how family ties vary with the environment, and how this affects economic outcomes. (JEL D13, D64, J12, Z13)

International audience; The year 2008 marks Amartya Sen's 75th birthday. Amartya has made deep and lasting contributions to the academic disciplines of economics, philosophy, and the social sciences more broadly. He has engaged in policy dialogue and public debate, advancing the cause of a human development focused policy agenda, and a tolerant and democratic polity. This argumentative Indian has made the case for the poorest of the poor, and for plurality in cultural perspective. It is not surprising that he has won the highest awards, ranging from the Nobel Prize in Economics to the Bharat Ratna, India's highest civilian honor. This public recognition has gone hand in hand with the affection and admiration that Amartya's colleagues and students hold for him. This is the second book in a two-volume Festschrift for Amartya Sen. The chapters, from across a range of social science disciplines, are written by some of the world's leading thinkers. This second book covers the topics of human development and capabilities; gender and household; growth, poverty, and policy; and society, politics, and history. It is a fitting tribute to Sen's own contributions to the discourse on society, institutions and development.