Testing for the Mean Reversion of Chinese Coal Stock Prices

Abstract

Aims: The main purpose of this paper is to test if prices of coal firm stocks in the Chinese A-Share market fluctuate around a long-term trend. Study Design: Existence of a unit root implies that a macroeconomic variable is non stationary and a shock to the market may have imposed a permeant effect on the long-run trend. The variable will not be mean-reverting. To improve the test robustness, conventional unit root tests must be conducted in line with structural break tests. A comparison of the unit roots of stock prices of two coal producing and processing firms in China’s Shanxi Province may lead us to conclude whether the market is trend-reverting. Place and Duration of Study: The study used stock prices of two coal-related firms that come from Shanxi Province, China. The Shanxi Coking Co., Ltd registers in Lingfeng. The Shanxi Xishan Coal and Electricity Power Co., Ltd registers in Taiyuan. Data was the monthly prices. The data period was from August 1996 to July 2014 for the Shanxi Coking, and from July 2000 to October 2015 for the Shanxi Xishan Coal and Electricity Power. Methodology: The paper conducted a unit root test applying regular ADF and PP techniques. Also, it carried out a structural break test using the Perron test and the Zivot-Andrews test (Model C). Results: Tests suggest that prices of two coal stocks are stationary series and these two series contain a shift between 2007 and 2008. The coal stock market may be weak-form efficient. Conclusion: Dramatic coal price fluctuations in China have not produced an enduring effect on prices of the coal stocks examined in the study. The coal-electricity price linkage could account for the trend reversion of coal firm stock prices.  Investors could profit to some extent from trading on coal equities. However, the paper suggests more and panel unit root tests for coal stock prices.