The study in Part I focuses on the impact of air quality index on stock market. First, the emotional instability of individual investors caused by air pollution may have an impact on their investing decisions; second, the change or enforcement of government policy may affect the corporate decision makers. The negative effect on stock returns caused by air pollutants is not significant, but the influence on turnover rate of the air quality is slightly bigger than on the stock returns. The study in Part II carried out empirical research on the dairy trade by state. The estimate outcome found that regulatory filing and trade tariffs have a significant impact on imports of dairy products. The study in Part III focuses on Equity Market Linkages and Decoupling Debate. The results of this study suggest that it is too soon to conclude that the Asian economies have decoupled from the advanced economies. The study in Part IV aims to provide a new theory of business cycle synchronization, in a framework that integrates value added trade, equity market linkages and industrial structure, which has important theoretical significance and practical application value.