What Moves Stock Prices? An Approach on the Influence of News on Stock Market

This research analyzed the trading days of the Bolsa de Valores de Sao Paulo (stock exchange of Sao Paulo), between 1990 to 2011, and selected the highest ups and downs. The inspiration of the project was the work of Cutler et al. (1989). Verifying the behavior of stock prices, we searched the cause of this variation. Despite the small variation of the average daily stock index on the period analyzed (mean daily variation of 0.29%), it can be noticed that in some trading days the stock market is highly volatile, with significant variations in asset prices. The KS test for series showed that the data cannot be approximated to a normal curve because of the fat tails. The empirical analysis shows that the highest decrease in the Brazilian stock market are associated with the Collor Plan, the president impeachment political crisis, the Real plan, the currency crisis and the subprime crisis. The largest increases occurred with the Collor Plan, the inauguration of President Itamar, the Real plan, the currency crisis and subprime. It was noticed that there is a temporal coincidence in times of high and further drops in the stock market. Another important aspect is that in the early years of the sample it was observed the preponderance of internal factors, in recent years, external factors stand out, due to the increase of the foreign investment in Bovespa.