The fact that stock market returns in Europe and the USA are characterised by conditional heteroscedasticity is by now well documented in a large literature. We address the question of whether the same is true of the four Chinese stock markets (Shanghai and Shenzhen A and B) over the period from 25 November 1994 to 27 April 2001. Using daily index data, we make two departures from the standard GARCH(1,1) model. First, we use exponential GARCH (EGARCH) to allow for asymmetry in the volatility, which may be present as a result of leverage effects. Second, we respond to evidence of two-way causality between volume and return (and return volatility) by introducing a simultaneous equation model of the relationship. The results of estimating the model indicate that asymmetry does not seem to be present to a significant degree, possibly as a result of lack of information or concern among Chinese investors. We find that volume appears to play a significant part in determining index volatility, which may reflect information arrival effects or may alternatively result from the direct impact of trading on volatility. At the same time, we also find that both the level of returns and their conditional variance have an impact on trade volume, probably because positive (negative) returns tend to attract (deter) investors into the markets.
