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Zitis PI, Kakinaka S, Umeno K, Stavrinides SG, Hanias MP, Potirakis SM. The Impact of COVID-19 on Weak-Form Efficiency in Cryptocurrency and Forex Markets. ENTROPY (BASEL, SWITZERLAND) 2023; 25:1622. [PMID: 38136502 PMCID: PMC10743358 DOI: 10.3390/e25121622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 12/24/2023]
Abstract
The COVID-19 pandemic has had an unprecedented impact on the global economy and financial markets. In this article, we explore the impact of the pandemic on the weak-form efficiency of the cryptocurrency and forex markets by conducting a comprehensive comparative analysis of the two markets. To estimate the weak-form of market efficiency, we utilize the asymmetric market deficiency measure (MDM) derived using the asymmetric multifractal detrended fluctuation analysis (A-MF-DFA) approach, along with fuzzy entropy, Tsallis entropy, and Fisher information. Initially, we analyze the temporal evolution of these four measures using overlapping sliding windows. Subsequently, we assess both the mean value and variance of the distribution for each measure and currency in two distinct time periods: before and during the pandemic. Our findings reveal distinct shifts in efficiency before and during the COVID-19 pandemic. Specifically, there was a clear increase in the weak-form inefficiency of traditional currencies during the pandemic. Among cryptocurrencies, BTC stands out for its behavior, which resembles that of traditional currencies. Moreover, our results underscore the significant impact of COVID-19 on weak-form market efficiency during both upward and downward market movements. These findings could be useful for investors, portfolio managers, and policy makers.
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Affiliation(s)
- Pavlos I. Zitis
- Department of Electrical and Electronics Engineering, University of West Attica, Ancient Olive Grove Campus, Egaleo, 12241 Athens, Greece;
| | - Shinji Kakinaka
- Department of Applied Mathematics and Physics, Graduate School of Informatics, Kyoto University, Sakyo, Kyoto 606-8501, Japan; (S.K.); (K.U.)
| | - Ken Umeno
- Department of Applied Mathematics and Physics, Graduate School of Informatics, Kyoto University, Sakyo, Kyoto 606-8501, Japan; (S.K.); (K.U.)
| | - Stavros G. Stavrinides
- Department of Physics, International Hellenic University, 65404 Kavala, Greece; (S.G.S.); (M.P.H.)
| | - Michael P. Hanias
- Department of Physics, International Hellenic University, 65404 Kavala, Greece; (S.G.S.); (M.P.H.)
| | - Stelios M. Potirakis
- Department of Electrical and Electronics Engineering, University of West Attica, Ancient Olive Grove Campus, Egaleo, 12241 Athens, Greece;
- National Observatory of Athens, Metaxa and Vasileos Pavlou, Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, Penteli, 15236 Athens, Greece
- Department of Electrical Engineering, Computer Engineering and Informatics, School of Engineering, Frederick University, Nicosia 1036, Cyprus
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Zitis PI, Kakinaka S, Umeno K, Hanias MP, Stavrinides SG, Potirakis SM. Investigating Dynamical Complexity and Fractal Characteristics of Bitcoin/US Dollar and Euro/US Dollar Exchange Rates around the COVID-19 Outbreak. ENTROPY (BASEL, SWITZERLAND) 2023; 25:e25020214. [PMID: 36832580 PMCID: PMC9955772 DOI: 10.3390/e25020214] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 01/15/2023] [Accepted: 01/18/2023] [Indexed: 06/01/2023]
Abstract
This article investigates the dynamical complexity and fractal characteristics changes of the Bitcoin/US dollar (BTC/USD) and Euro/US dollar (EUR/USD) returns in the period before and after the outbreak of the COVID-19 pandemic. More specifically, we applied the asymmetric multifractal detrended fluctuation analysis (A-MF-DFA) method to investigate the temporal evolution of the asymmetric multifractal spectrum parameters. In addition, we examined the temporal evolution of Fuzzy entropy, non-extensive Tsallis entropy, Shannon entropy, and Fisher information. Our research was motivated to contribute to the comprehension of the pandemic's impact and the possible changes it caused in two currencies that play a key role in the modern financial system. Our results revealed that for the overall trend both before and after the outbreak of the pandemic, the BTC/USD returns exhibited persistent behavior while the EUR/USD returns exhibited anti-persistent behavior. Additionally, after the outbreak of COVID-19, there was an increase in the degree of multifractality, a dominance of large fluctuations, as well as a sharp decrease of the complexity (i.e., increase of the order and information content and decrease of randomness) of both BTC/USD and EUR/USD returns. The World Health Organization (WHO) announcement, in which COVID-19 was declared a global pandemic, appears to have had a significant impact on the sudden change in complexity. Our findings can help both investors and risk managers, as well as policymakers, to formulate a comprehensive response to the occurrence of such external events.
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Affiliation(s)
- Pavlos I. Zitis
- Department of Electrical and Electronics Engineering, University of West Attica, Ancient Olive Grove Campus, GR-12241 Aigaleo, Greece
| | - Shinji Kakinaka
- Department of Applied Mathematics and Physics, Graduate School of Informatics, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Ken Umeno
- Department of Applied Mathematics and Physics, Graduate School of Informatics, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Michael P. Hanias
- Department of Physics, International Hellenic University, GR-65404 Kavala, Greece
| | | | - Stelios M. Potirakis
- Department of Electrical and Electronics Engineering, University of West Attica, Ancient Olive Grove Campus, GR-12241 Aigaleo, Greece
- Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Metaxa and Vasileos Pavlou, GR-15236 Penteli, Greece
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Motion Tracking System for Robust Non-Contact Blood Perfusion Sensor. SENSORS 2018; 18:s18010277. [PMID: 29346298 PMCID: PMC5795823 DOI: 10.3390/s18010277] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 01/07/2018] [Accepted: 01/15/2018] [Indexed: 11/17/2022]
Abstract
We propose a motion-robust laser Doppler flowmetry (LDF) system that can be used as a non-contact blood perfusion sensor for medical diagnosis. Endoscopic LDF systems are typically limited in their usefulness in clinical contexts by the need for the natural organs to be immobilized, as serious motion artifacts due to the axial surface displacement can interfere with blood perfusion measurements. In our system, the focusing lens moves to track the motion of the target using a low-frequency reference signal in the optical data, enabling the suppression of these motion artifacts in the axial direction. This paper reports feasibility tests on a prototype of this system using a microfluidic phantom as a measurement target moving in the direction of the optical axis. The frequency spectra detected and the perfusion values calculated from those spectra show that the motion tracking system is capable of suppressing motion artifacts in perfusion readings. We compared the prototype LDF system’s measurements with and without motion feedback, and found that motion tracking improves the fidelity of the perfusion signal by as much as 87%.
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Humeau-Heurtier A, Mahe G, Durand S, Abraham P. Multiscale Entropy Study of Medical Laser Speckle Contrast Images. IEEE Trans Biomed Eng 2013; 60:872-9. [DOI: 10.1109/tbme.2012.2208642] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Humeau-Heurtier A, Buard B, Mahe G, Abraham P. Laser speckle contrast imaging of the skin: interest in processing the perfusion data. Med Biol Eng Comput 2011; 50:103-5. [DOI: 10.1007/s11517-011-0856-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 12/13/2011] [Indexed: 10/14/2022]
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Humeau A, Trzepizur W, Rousseau D, Chapeau-Blondeau F, Abraham P. Localization of transient signal high-values in laser Doppler flowmetry signals with an empirical mode decomposition. Med Phys 2008; 36:18-21. [DOI: 10.1118/1.3041168] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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