The Mainland-Hong Kong Stock Connect program is a globally unique institutional innovation. This partially open financial system is unparalleled worldwide. As the influence of the Mainland-Hong Kong Stock Connect on A-shares has grown, the volume of research literature has gradually increased, and studies on the policy impact from various sectors have become prevalent. Prior to the introduction of the Mainland-Hong Kong Stock Connect, studies indicated that A-share stock prices did not significantly react to stock information, indicating low informational content in stock prices. The Mainland-Hong Kong Stock Connect, through its moderate openness, has effectively introduced mature overseas investment philosophies and international capital, altering the investor structure of A-shares and impacting trading behavior. This paper aims to explore whether the initiation of the Mainland-Hong Kong Stock Connect policy positively affects the informational content of A-share stock prices under the aforementioned premises. To minimize the interference of short-term market fluctuations on the research, this paper uses the relatively long-term future earnings response as the entry point for studying the informational content of stock prices. Specifically, it first selects a full sample of Mainland-Hong Kong Stock Connect stocks to conduct annual cross-sectional regression and multi-year linear regression to examine changes in the informational content of stock prices before and after policy implementation. It then includes a control group of stocks not selected for the Mainland-Hong Kong Stock Connect, conducting multi-year linear regression analysis with the experimental group samples to investigate whether the policy initiation has improved the informational content of stock prices for Mainland-Hong Kong Stock Connect stocks compared to those not selected. The results show that after the initiation of the Mainland-Hong Kong Stock Connect policy, the informational content of stock prices increased for Shanghai Stock Connect but decreased for Shenzhen Stock Connect. Compared to stocks not selected for the Mainland-Hong Kong Stock Connect, the informational content of stock prices also increased for Shanghai Stock Connect and decreased for Shenzhen Stock Connect. Overall, the results of this study indicate that the Mainland-Hong Kong Stock Connect policy has indeed achieved its initial policy design goals, warranting further exploration into deepening openness to optimize the structure of the capital market.

Although margin trading has significant impacts on the stock market, extant research has mainly focused on its effect on stock price volatility and has rarely examined its influence on the rate of returns. In addition, little systematic research has examined the differential effects of margin trading under different circumstances. This thesis examines the effects of margin trading in bull market, bear market, balanced market and among stocks included in main board, SMEs(small and medium-sized enterprises) board, GEM(growth enterprises board), as well as large-cap and small-cap in China. I further studied the long-, medium-, and short-term influences of margin trading on the volatility of stock price, return rate, and liquidity of the market by both using the SVAR model and conducting panel data analyses.

The findings show that: a)Volatility. Margin trading can effectively curtail the medium- and short-term volatility of the share price under any market condition but has no prominent influence on long-term volatility. b)Profitability. Margin trading enhances profitability in the bull market with an apparent leverage effect while having no significant effects on short-term profitability in the balanced market and the bear market. c) Individual shares with different attributes. The influences of margin trading on the large-cap and small-cap shares, shares with high vs. low PE ratio, shares included in the main board and SMEs stocks vary in different types of market. d) Liquidity. The influences of margin trading on the fluidity of market are significantly different in the bull, bear, and balanced markets.

Finally, I set up a new trading strategy based on the above conclusions. The result from hypothetical trading demonstrates that the newly-created trading strategy works better than the long-term holding strategy, highlighting the practical implications of this thesis in addition to its implications for research