Paper Title
The Repeated Nonlinear Principal-Agent Model an Adapted Study by the Marginal Disutility of Labor and Fluctuations in Demand of Products of the Game with Infinite Horizon

Abstract
The relationship between principal and agent has been much discussed in the current literature because of its strategic importance in economic theory. The incentives present in this relationship, as well as the behavior of the stakeholders' interests, have a fundamental role in defining the best contract for both parties. Knowing this, this paper discusses the possibility of nonlinearity present in the marginal cost relation of the agents and quantity performed in each activity that decrease by increase rates the marginal gains of the agents in the principal-agent model. Moreover, positive changes in the quantity required not stipulated in contract can negatively influence the utility of the agents. As a result, these two factors tend to increase the monetary increments of the principal to maintain the desired productivity. Besides that, this paper illustrates the necessity to analyze the gains of the agents and the principal given that this game is played repeatedly. In a repeated principal-agent game in which each player's criterion is his long-run average expected utility, efficient behavior can be sustained by a Nash equilibrium if it is Pareto-superior to a one-period Nash equilibrium. The model and the numerical example constructed in this paper demonstrate the need to adapt the main agent model to situations in which both previously explained factors are present. Keywords - Incentives, Principal-Agent Model, Marginal Disutility of labor, Repeated Games.