Aplicabilidade dos preceitos teóricos da hipótese dos mercado eficientes na variação da cotação diária de ações: estudo de caso do grupo Casas Bahia

Abstract

This study investigated, through a case study, whether fluctuations in the stock price of Grupo Casas Bahia (BHIA3) reflect any of the forms of efficiency proposed by the Efficient Market Hypothesis (EMH). The analysis focused on major outliers in the stock’s price movements compared to variations in the São Paulo Stock Exchange Index (IBOV), with the aim of determining whether these anomalies were driven by new and publicly available market information. Employing an exploratory, qualitative, and comparative methodology—using Magazine Luiza (MGLU3) as a benchmark—the study found that, overall, price variations tend to align with available information, suggesting the presence of weak-form or semi-strong-form market efficiency. However, the analysis also identified delays in the incorporation of information and price reactions whose magnitude was disproportionate to the underlying events, indicating episodes of market inefficiency. Ultimately, the findings suggest that while the market generally responds coherently to new information, it does not always do so in an immediate or proportionate manner, thereby exposing both opportunities and risks that should be carefully considered by investors and analysts in their decision-making processes.