SUMMARY
Stock exchange automation, characterized by the replacement of floor trading systems by electronic trading systems, is one of the main restructuring processes observed in global capital markets in recent decades. This paper investigates the effects of automation in the São Paulo Stock Exchange (B3), which adopted an electronic trading system in October 2005. Empirical analysis of the Bovespa index rejects the random walk hypothesis for the periods before and after B3 automation, and provides evidence of distinct volatility regimes. After automation, there is an increase in the linear dependence of IBovespa returns, suggesting a negative effect of automation on the Brazilian stock market’s efficiency. On the other hand, in the same period, there is evidence for a reduction in the long-term persistence of conditional volatility, in response to shocks to returns.