Résumé
Investors can use segment information in order forecast risk and return of diversified and/or multinational firms. This thesis contributes to develop and improve this information use on a financial point of view. The quality and the form of the segment information disclosed by a firm depend on some characteristics of this firm: diversification, internal organization (organizational structure, vertical integration), outline (size, capital market activity, minority interest, leverage, political sensitivity and return on investment of its industries) and the data availability. This thesis proposes a general frame of the use of this information depending on the approach of the users and the quality of this information. Furthermore, this thesis proposes an application of this use in a mechanical model of earning forecasts. These theoretical propositions are tested in four empirical studies. Two of them are international ones.