Evidências de bolhas de preços no mercado acionário brasileiro




Currently, the existence of bubbles in asset pricing has been the cause of great concern for government authorities and investors in countries with relevant capital markets. The existence of a bubble component in asset pricing can be inferred by its deviation with respect to its fundamental value. When it comes to stocks, the suspicion about a price bubble arises when stock prices deviate relative to dividends in the long run. The present study aimed at finding evidence on price bubble episodes in the Brazilian stock market from 1994 to 2007. Tests were carried out considering the stock market as a whole and also in stocks of 17 industrial sectors classified in Economaticas database. In order to test the evidence of bubbles in the market as a whole, the Bovespa average stock market index (Ibovespa) was used as a proxy of the average stock market price and an average dividend index was built based on Ibovespas stock portfolios in the period. Engle-Granger and Johansen cointegration tests were performed with the purpose of verifying whether the above mentioned indexes kept a long run equilibrium relationship. Our findings show that there is no evidence of cointegration between the Bovespa stock index and the Bovespa dividend index, which means that the two series have not kept a long run equilibrium relation indicating the possibility that one or more bubbles might have occurred during the focused period. The industrial sector tests show results similar to the general test, indicating strong evidence on the possibility of price bubbles in the 17 industry sectors analyzed. Aiming at yielding more robustness to the results, Granger causality tests were also carried out considering the market as a whole and by industrial sector. The theoretical assumption is that if the stock price is a function of dividends, the latter should Granger-cause (lead) the former. The Granger causality tests indicate that dividends do not Granger-cause Ibovespa and in the 17 industrial sectors, at the significance level of 1%, 82% of the sectors did not show any causality in the dividend price direction, which confirms the results obtained in the cointegration tests.


stock prices bolhas de preços cointegration dividendos causalidade granger granger causality preços das ações cointegração price bubbles ciencias contabeis dividends

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