Comparative Statics for Market Games: The Strong Concavity Case

In this paper we study the effects of a change in sorne exogenous variable (the number of players or a parameter in the payoff functions) on the strategies played and payoffs obtained in a Nash Equilibrium in the framework of a Market Game (a generalization of the Cournot model)o We assume a strong concavity condition which implies that the best reply function of any player is decreasing on sum of the strategies of the remaining players (Le. strategic substitution). Our results generalize and unify those known in the Cournot model

Welfare losses under cournot competition

We find that in a market for a homogeneous good where firms are identical, compete in quantities and produce with constant returns, the percentage of wel-fare losses (PWL) is small with as few as five competitors for a class of demand functions which includes linear and isoelastic cases. However with fixed costs and asymmetric firms PWL can be large. We provide exact formulae of PWL and robust constructions of markets were PWL is close to one in these two cases. We show that the market structure that maximizes PWL is either monopoly or dominant firm, depending on demand. Finally we prove that PWL is minimized when all firms are identical, a clear indication that the assumption of identical firms biases the estimation of PWL downwards

The Long-Run Keynesian Multiplier

We study the impact of investment on employment. In the short−run an increase in investment stimulates employment (this is the standard Keynesian multiplier). However increases of investment translate into increases in the capital stock. If labor and capital are substitutes (resp. complements), an increase in investment today decreases (resp. increases) employment tomorrow. We provide a formula to measure the overall effect of an increase in investment on emplyment, assuming that certain regularities hold.Publicad

Differentiable comparative statics with payoff functions not differentiable everywhere

In this note we consider Cournot oligopoly. Due to the consideration of several consumers and/ or technologies, the profit function is not differentiable everywhere. We show that Cournot equilibrium never occurs in outputs where profit functions are not-differentiable. This result validates the procedure of differentiating profit functions to perform comparative statics in models where profit functions are not differentiable everywhere.Publicad

Monk business: an example of the dynamics of organizations.

In this paper we present a dynamic model of an organization. It is shown that the quality of the members of the organization may cycle and that even if the organization promotes excellency, the organization may end up populated by mediocre agents only.Overlapping generations; Quanty organization;

Peace agreements without commitment

In this paper we present a model of war between two rational and completely informed players. We show that in the absence of binding agreements war can be avoided in many cases by one player transferring money to the other player. In most cases, the "rich" country transfers part of her money to the "poor" country. Only when the military proficiency of the "rich" country is sufficiently great, it could be that the "poor" country can stop the war by transfering part of its resources to the "rich" country

Robust implementation under alternative information structures

In this paper we consider a model in which agents have complete information about their neighbours and, possibly, incomplete information about the rest of the economy. We consider two different informational frameworks. In the first, agents do not have priors about what is going on in the rest of the economy. In the second, agents are supposed to have priors about the unknown characteristics. We present a mechanism which any social choice correspondence satisfying monotonicity and no veto powet in both informational settings for every possible prior thus requiring little knowledge from the point of view of the designer of the information possesed by agents about the economy

Rational Sabotage in Cooperative Production with Heterogeneous Agents

We present a model of cooperative production in which rational agents might carry out sabotage activities that decrease output. We provide necessary and sufficient conditions for the existence of a Nash equilibrium without sabotage. It is shown that the absence of sabotage in equilibrium depends on the interplay between technology, relative productivity of agents and the degree of meritocracy. In particular we show that, ceteris paribus, meritocratic systems give more incentives to sabotage than egalitarian systems.Publicad

Implementation of the Walrassian Correspondance by Market Games

In this paper we present a set ofaxioms guaranteeing that, in exchange economies with or without indivisible goods, the set of Nash, Strong and active Walrasian Equilibria aH coincide in the framework of market games

Comparative Statics in Cournot Free Entry Equilibrium

In this paper we study the effects of a change in an exogenous variable (the fixed cost or a parameter in the demand function) on the output and the number of active firms in a Symmetric Cournot Equilibrium with Free Entry (SCEFE). The results obtained here are different from those obtained in the Cournot model with a given number of firms. In particular, an increase in demand might yield a decrease in the output of the industry.We also show that any observation on prices, profits and number of firms is compatible with the assumption that the market is in a SCEFE. If fixed costs can be observed, there is a loose relationship between the profit rate and the number of active firms. This result is used as a warning against the use of the profit rate as a measure of an anticompetitive position and against the Structure–Conduct– Performance paradigm.Publicad