自2008年金融海嘯與2009年的歐債危機後，全世界的金融市場陷入空前低迷，經濟狀況趨向悲觀，台灣股市也無法幸免於難。金管會為了刺激經濟，振興台灣股市，分別於2013年9月23日施行了平盤以下可放空股票以及2014年1月6日開放現股當沖的兩項新政策，期望能提升台灣股市的成交量，帶動整體經濟情勢向上攀升，促使經濟能逐漸好轉。
本文使用了Lo and Mackinlay (1988)的參數型變異數比率檢定，接著以Wright (2000)以rank與sign為基礎之非參數變異數比率檢定，最後以Chow and Denning (1993)之多重變異數比率來檢定，並針對此兩項新制度施行的前後三個月來作分析。由實證結果得知，在此兩項新制度施行後，約有五成的股票顯示由拒絕弱效率市場假說轉為接受此假說，尤以電子類股更加明顯。由此可知，當開放平盤以下可放空股票與現股當沖後，對於部份的股票市場效率性的確有所提升。
Due to economic crisis in 2008 and the European debt crisis in 2009, the financial markets around the world has became an unprecedented low and economic status has tended to misery, which resulted in having a narrow escape in the Taiwan stock market. In order to stimulate the economy and boost Taiwan's stock market, FSC conducted that the stock opens below the flat in September 23, 2013 and the day trading of stock in January 6, 2014. With two new policies, they will improve Taiwan's stock market volume, drive upward overall economic situation, and prompt the economy to have the turnover gradually.
The essay adopted the Lo and Mackinlay (1988) “parametric variance ratio test," Wright (2000) “rank and sign-based nonparametric variance ratio test,” and Chow and Denning (1993) “multiple variance ratio to test.” Meanwhile, we analyzed the new sys-tem of three months before and after the implementation. After the implementation of two new systems, about 50 percent of the stock showed that the inventors accept this hypothesis instead of rejecting weak-form efficient market. Especially, the electronics is more apparent. As a result, the open stock below the flat and the day trading of stock are efficient and boosting for some parts of stock market indeed.
