The objetctive of this paper is to present evidence of weak efficiency in the Brazilian stock market. Contrary to other studies in the Brazilian literature on the topic, the statistical procedure always test the validity of the underlying hypotheses of the test statistics employed. Based on a sample of IBOVESPA index stocks for the recent period, the relevance of linear and non-linear autoregressive terms and day-of-the-week and holiday effects to the forecast of stock returns is studied. The results suggest that in most stocks some of the mentioned effects are present, in particular a Tuesday effect.
efficiency tests; Brazilian stock market; returns forecast; day-of-the-week effects; specification tests
