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COAR Access Rights: metadata only accessSubject: Market efficiency

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    Article
    Citation - WoS: 9
    Citation - Scopus: 9
    Market Development and Market Efficiency: Evidence Based on Nonlinear Panel Unit Root Tests
    (Routledge Journals, Taylor & Francis Ltd, 2019) Aktan, Ceyda; Iren, Perihan; Omay, Tolga
    This study tests the weak form market efficiency of 32 European stock markets. Utilizing monthly data from June 2006 to June 2017, six different, newly developed nonlinear panel root tests were applied in three different groups of European markets: Frontier, Emerging and Developed. The results show that there is a meaningful relationship between different levels of economic development and the weak form market efficiency. Considering the nonlinear structure of the stock market indices, use of linear models might lead to wrong conclusions regarding market efficiency. Using several nonlinear panel root tests, the results of this study shed more light on the true data generating process of the stock market indices and more appropriately model market efficiency.
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    Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Examining the non-linear stochastic behavior of the European energy market: evidence from nonlinear unit root tests
    (Taylor & Francis inc, 2022) Aktan, Ceyda; Omay, Tolga; Sahin, Eyyup Ensari
    Stock market efficiency has been one of the most investigated topics of the last century. Knowing the efficiency of a market has major implications for both investors and policymakers, as a perfectly efficient market eliminates any arbitrage opportunity and the possibility of actually beating the market. For this reason, this study aims to examine the weak-form market efficiency of the European energy markets using linear and nonlinear unit root tests for the period covering February 2012 to April 2021. The results indicated that while the Augmented Dickey-Fuller test captured the stationarity in only Austria's Oil, and Gas index, using nonlinear tests showed stationarity in 17 of the 20 indices tested. Overall, the European Energy Market can be considered inefficient under the weak form of the Efficient Market Hypothesis. Therefore, there is an indication of profitable arbitrage opportunities among energy stocks. Signs of stationarity also suggest that shocks to energy stocks will have temporary effects. Energy markets of Austria, Finland, France, Greece, Italy, Netherlands, Russia, Spain, Sweden, and the United Kingdom, for this reason, could benefit from policy changes to support increased information flow to achieve more transparency and utilize better trading technologies.
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    Conference Object
    Nonlinearity in Emerging European Markets: Pre and Post Crisis Periods
    (Springer Science and Business Media B.V., 2019) Aktan,C.; Omay,T.
    Investigating the efficiency of emerging markets has been a popular research trend in the past decade, showing implications on both the economy and the policies of the countries in question. Market efficiency, in other words, informational efficiency, states that if markets are fully efficient, then all information is instantly reflected the prices of stocks. However, there are many arguments for and against this theory, especially on the discussions of the 2008 Global Financial Crisis. These past studies are seen to be showing mixed results. It is important the note that there is a nonlinear movement among the stock prices within stock markets and this needs to be incorporated in the tests that are used to measure their efficiency in order to obtain more accurate results. Therefore, in this study, we have tested the weak form efficiency of the emerging markets located in Europe, namely, Czech Republic, Greece, Hungary, Poland, Turkey, and Russia. Effects of the 2008 Global Financial Crisis were put forward by taking two different time periods (Pre: November 2005–September 2008 and Post: October 2008–February 2019—Crisis) and applying newly developed nonlinear unit root tests. Results of the study supported previous research and showed that the efficiency of most markets changed in the post-crisis period from efficient to inefficient. © 2019, Springer Nature Switzerland AG.