A eficiência de mercado e a crise mundial de 2008

Abstract

To test the market efficiency in its weak form allows demonstrating the predictability of the assets price, giving the possibility of extraordinary profits without risk, simply by analyzing the time series of the asset. In a situation of financial crisis the behavior of asset prices can be changed, since they are susceptible to human emotions. In 2008, there was a global crisis due to the U.S. financial market decline. This research test whether the crisis has changed the market efficiency, stock indices by some developed and developing countries, belonging to the continents: American, Asian and European in the period of January 1st 2007 to June 30th 2010. The objective is to test the market efficiency in pre and post-crisis. Being able to define the start of a financial crisis at any time when a situation is abnormal, dangerous and present marked impairment. Historically, the global crisis commencement was stipulated on September 15th 2008, for all indices showed a decline, but by analyzing the time series of indices, it was noted that this is not the date that the indices showed the biggest drop. This research finds three possible dates that could be considered the beginning of this crisis and tests the market efficiency for each. To this end, it was still necessary to treat the sub-period analysis for the third time found a way completely different from the previous two. The test used was the ratio of the variance described by Lo and MacKinlay (1988). The search result showed inefficiency of the market, demonstrating the predictability for most indexes.