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Adaptive market hypothesis: The story of the stock markets and COVID-19 pandemic

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  • Okorie, David Iheke
  • Lin, Boqiang

Abstract

Since the level of markets’ information efficiency is key to profiteering by strategic players, Shocks; such as the COVID-19 pandemic, can play a role in the nature of markets’ information efficiency. The martingale difference and conditional heteroscedasticity tests are used to evaluate the Adaptive form of market efficiency for four (4) major stock market indexes in the top four affected economies during the COVID-19 pandemic (USA, Brazil, India, and Russia). Generally, based on the martingale difference spectral test, there is no evidence of a substantial change in the levels of market efficiency for the US and Brazilian stock markets in the short, medium, and long term. However, in the long term, the Indian stock markets became more information inefficient after the coronavirus outbreak while the Russian stock markets become more information efficient. Intuitively, these affect the forecastability and predictability of these markets’ prices and/or returns. Thereby, informing the strategic and trading actions of stock investors (including arbitrageurs) towards profit optimization, portfolio asset selection, portfolio asset adjustment, etc. Similar policy implications are further discussed.

Suggested Citation

  • Okorie, David Iheke & Lin, Boqiang, 2021. "Adaptive market hypothesis: The story of the stock markets and COVID-19 pandemic," The North American Journal of Economics and Finance, Elsevier, vol. 57(C).
  • Handle: RePEc:eee:ecofin:v:57:y:2021:i:c:s1062940821000322
    DOI: 10.1016/j.najef.2021.101397
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    Cited by:

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    6. Khalid Alkhatib & Mothanna Almahmood & Omar Elayan & Laith Abualigah, 2022. "Regional analytics and forecasting for most affected stock markets: The case of GCC stock markets during COVID-19 pandemic," International Journal of System Assurance Engineering and Management, Springer;The Society for Reliability, Engineering Quality and Operations Management (SREQOM),India, and Division of Operation and Maintenance, Lulea University of Technology, Sweden, vol. 13(3), pages 1298-1308, June.
    7. Jacek Karasinski, 2022. "The Impact of the COVID-19 Outbreak on the Weak-Form Informational Efficiency of the Warsaw Stock Exchange (Wplyw wybuchu epidemii COVID-19 na efektywnosc informacyjna Gieldy Papierow Wartosciowych w ," Research Reports, University of Warsaw, Faculty of Management, vol. 2(37), pages 15-28.
    8. Okorie, David Iheke & Lin, Boqiang, 2023. "Cryptocurrency spectrum and 2020 pandemic: Contagion analysis," International Review of Economics & Finance, Elsevier, vol. 84(C), pages 29-38.
    9. Muhammad Danial & Nadia Iftikhar & Syed Quaid Ali Shah, 2023. "Analyzing the Performance of Pakistan Equity Mutual Funds Using Multifactor Models: Pre-COVID Analysis," Business Management and Strategy, Macrothink Institute, vol. 14(2), pages 296-328, December.
    10. Deniz Erer & Elif Erer & Selim Güngör, 2023. "The aggregate and sectoral time-varying market efficiency during crisis periods in Turkey: a comparative analysis with COVID-19 outbreak and the global financial crisis," Financial Innovation, Springer;Southwestern University of Finance and Economics, vol. 9(1), pages 1-25, December.
    11. Ferreira, Joaquim & Morais, Flávio, 2023. "Predict or to be predicted? A transfer entropy view between adaptive green markets, structural shocks and sentiment index," Finance Research Letters, Elsevier, vol. 56(C).
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    13. Muhammad Naeem Shahid, 2022. "COVID-19 and adaptive behavior of returns: evidence from commodity markets," Palgrave Communications, Palgrave Macmillan, vol. 9(1), pages 1-15, December.
    14. Wang, Xiaoyang, 2022. "Efficient markets are more connected: An entropy-based analysis of the energy, industrial metal and financial markets," Energy Economics, Elsevier, vol. 111(C).
    15. Fatemeh Rahimzadeh & Hamed Pirpour & Bahman P. Ebrahimi, 2022. "The impact of economic sanctions on the efficiency of bilateral energy exports: the case of Iran," SN Business & Economics, Springer, vol. 2(9), pages 1-18, September.
    16. Espinosa-Paredes, G. & Rodriguez, E. & Alvarez-Ramirez, J., 2022. "A singular value decomposition entropy approach to assess the impact of Covid-19 on the informational efficiency of the WTI crude oil market," Chaos, Solitons & Fractals, Elsevier, vol. 160(C).

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    More about this item

    Keywords

    Martingale; Heteroscedasticity; Market efficiency hypothesis; Hypothesis testing; COVID-19 pandemic;
    All these keywords.

    JEL classification:

    • C12 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods and Methodology: General - - - Hypothesis Testing: General
    • G01 - Financial Economics - - General - - - Financial Crises
    • G10 - Financial Economics - - General Financial Markets - - - General (includes Measurement and Data)
    • G14 - Financial Economics - - General Financial Markets - - - Information and Market Efficiency; Event Studies; Insider Trading

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