Viés e incertezas que cercam os laudos de avaliação: análise da oferta pública de ações Magnesita refratários S.A.

The issuance of an appraisal report becomes mandatory when the Public Offer for Acquisition of Shares OPA. Endowed with subjectivity, these valuation reports are guides for assigning value to an entity. This research had the objective of analyzing an appraisal report issued in 2007. To achieve this goal, Magnesita S.A., an industry engaged in the production of refractories for the steel and cement industries, was randomly selected. The expected result of the valuation of a company is to attribute, by means of specific methods, value to an entity. This value should be free of bias and pre-judgments on the part of the analysts so that this value adequately reflects the company in its qualitative and quantitative aspects. However, it is possible to say that the market is not as rational and well-informed as the studies on the theory of market efficiency show. In fact, it is formed by individuals who search for results in a very peculiar way, based on realities built according to their life experience, the possibility of access to information and personal interests. Key-words: Valuation reports; company valuation; market efficiency.