L’allocation des risques dans les contrats : de l'économie des contrats « incomplets » à la pratique des contrats administratifs

L'allocation des risques inhérents à l'exécution d'obligations dans des accords dont la temporalité est longue est une question importante, notamment pour l'économie. Or, à cet égard, il est significatif de constater que les entrées consacrées au droit administratif dans l'Encyclopedia of Law and Economics ne font pas mention des contrats administratifs, et que les entrées relatives au droit des contrats ne renvoient jamais au droit administratif. On ne peut que signaler, à ce propos, l'originalité de l'ouvrage de microéconomie des marchés publics et de la réglementation de J.-J Laffont et J. Tirole (1993). Quelles conclusions tirer de ce constat ? De notre point de vue, deux hypothèses peuvent être avancées : soit les économistes se désintéressent des contrats administratifs, soit ils les intègrent implicitement dans le même moule que les contrats de droit privé. Nous estimons que la deuxième hypothèse est la plus plausible, et nous souhaitons l'explorer ici en réfléchissant sur le fait de savoir si le droit positif des contrats privés et administratifs rend possible l'application de mêmes catégories d'analyse en matière d'allocation des risques. Cette question appellera naturellement une réflexion sur la signification et la portée empirique de la notion économique d'incomplétude des contrats.Risk allocation in contracts : from the economics of incomplete contracts to the effective practices in administrative contracts Risk allocation in contracts is an important issue for both economics and law. It questions the theoretical, methodological, and empirical foundations of economic and legal analysis. It also offers a valuable ground for comparative legal-economic inquiry. The article aims at providing some insights into that general approach, and proceeds with an articulation of theoretical and empirical analysis. The paper first offers a critical analysis of some key economics based hypothesis on law, contract law and legal institutions, notably the courts. It concentrates on various components of the New Institutional Economics stream that have something to do with the notion of contractual incompleteness. The emphasis is put on two central issues : the contract~institutions relationship, and the scope of incompleteness as a guide for empirical research into the economic dimensions of contract law. The second part of the article compares and evaluates the significance of the economic concept of incompleteness and the French legal notion of imprévision, which relates to a notion that the administrative courts have set up to decide cases in which the occurrence of unforeseen events affects the contractual equilibria as set up ex ante. The analysis then moves toward the research of a legal and empirical translation of uncertainty of the future. The article argues that positive legal provisions in contract law enable co-contractors to set up a framework in which the consequences of unforeseen events can be addressed. Legal provisions such as those which relate to conditional duties, aleatory contracts, force majeure, fortuitous events, price revision, hardship, are examples of tools that allow a significant amount of previsibility in contractual relations, particularilly longterm contracts. We then offer an empirical analysis of a specific legal notion : imprévision. The analysis is based on legal data, namely the French Conseil d’État decisions that deal with a request for compensation by the State of the economic consequences of the occurrence of unforeseen events for the suppliers. A descriptive statistical analysis is associated to a study of the legal instructions given by the State to its contracting officers ; a comparison of price determination provisions under American procurement and French law of marchés publics is then made.ou