This paper examines the impact of CITIC Securities (CITICS)’ insider trading on five state-owned banks’ stock returns in China. We first conduct a structural Vector Autoregression model together with Granger causality to investigate the response of banks’ returns to that of CITICS. Next an Exponential Generalised AutoRegressive Conditional Heteroskedasticity process is employed to capture the volatilities of stock returns, and therefore investigate the response of five banks to that of CITICS. The dataset for three months after the scandal is obtained and the estimation results show some significant coupling effects do exist within stock returns of financial sector in stock market as well as within their volatilities. The core findings in this study suggest that Chinese stock prices could reflect all relevant information available from past changes in the share price as well as publicly available information. To some extent, China’s stock market is semi-strong efficiency, implying the quality of investors’ rationality and providing regulators with empirical evidence to policy-making.
