IDEAS home Printed from https://ideas.repec.org/a/eee/finlet/v73y2025ics1544612324016738.html
   My bibliography  Save this article

How fake news effects spread in an oligopolistic market — Evidence from the insulin market

Author

Listed:
  • Louchez, Aniss

Abstract

This study analyzes the impact of an event on November 11, 2022, when a fake “certified” Twitter account falsely claimed that Eli Lilly's insulin would be provided for free. We examine spillover effects on competitors within the insulin market oligopoly. Our findings reveal that while competitors experienced short-term impacts, these were weaker and of shorter duration compared to Eli Lilly. Spillovers within the broader pharmaceutical sector were limited to the immediate aftermath. No anticipatory behavior was detected. The effects were confined to American stock exchanges, suggesting an absence of spillovers in European markets.

Suggested Citation

  • Louchez, Aniss, 2025. "How fake news effects spread in an oligopolistic market — Evidence from the insulin market," Finance Research Letters, Elsevier, vol. 73(C).
    • Handle: RePEc:eee:finlet:v:73:y:2025:i:c:s1544612324016738
    DOI: 10.1016/j.frl.2024.106644
    as

    Download full text from publisher

    File URL: http://www.sciencedirect.com/science/article/pii/S1544612324016738
    Download Restriction: Full text for ScienceDirect subscribers only
    File URL: https://libkey.io/10.1016/j.frl.2024.106644?utm_source=ideas
    LibKey link: if access is restricted and if your library uses this service, LibKey will redirect you to where you can use your library subscription to access this item
    ---><---

    As the access to this document is restricted, you may want to

    for a different version of it.

    References listed on IDEAS

    as
    1. Xu, Libo, 2021. "Stock Return and the COVID-19 pandemic: Evidence from Canada and the US," Finance Research Letters, Elsevier, vol. 38(C).
    2. Martin Shubik, 1973. "Information, Duopoly And Competitive Markets: A Sensitivity Analysis," Kyklos, Wiley Blackwell, vol. 26(4), pages 736-761, November.
    3. Boido, Claudio & Aliano, Mauro, 2023. "Digital art and non-fungible-token: Bubble or revolution?," Finance Research Letters, Elsevier, vol. 52(C).
    4. Arcuri, Maria Cristina & Gandolfi, Gino & Russo, Ivan, 2023. "Does fake news impact stock returns? Evidence from US and EU stock markets," Journal of Economics and Business, Elsevier, vol. 125.
    5. Hwang, Hae-shin, 1995. "Information Acquisition and Relative Efficiency of Competitive, Oligopoly and Monopoly Markets," International Economic Review, Department of Economics, University of Pennsylvania and Osaka University Institute of Social and Economic Research Association, vol. 36(2), pages 325-340, May.
    6. Taichi Murayama & Shoko Wakamiya & Eiji Aramaki & Ryota Kobayashi, 2021. "Modeling the spread of fake news on Twitter," PLOS ONE, Public Library of Science, vol. 16(4), pages 1-16, April.
    7. Aoyagi, Masaki, 2002. "Collusion in Dynamic Bertrand Oligopoly with Correlated Private Signals and Communication," Journal of Economic Theory, Elsevier, vol. 102(1), pages 229-248, January.
    8. Corrado, Charles J., 1989. "A nonparametric test for abnormal security-price performance in event studies," Journal of Financial Economics, Elsevier, vol. 23(2), pages 385-395, August.
    9. Boehmer, Ekkehart & Masumeci, Jim & Poulsen, Annette B., 1991. "Event-study methodology under conditions of event-induced variance," Journal of Financial Economics, Elsevier, vol. 30(2), pages 253-272, December.
    10. Fama, Eugene F, et al, 1969. "The Adjustment of Stock Prices to New Information," International Economic Review, Department of Economics, University of Pennsylvania and Osaka University Institute of Social and Economic Research Association, vol. 10(1), pages 1-21, February.
    11. Ellis, Randall P. & Martins, Bruno & Zhu, Wenjia, 2017. "Health care demand elasticities by type of service," Journal of Health Economics, Elsevier, vol. 55(C), pages 232-243.
    12. Elsas, Ralf & Schoch, Daniela Stephanie, 2023. "Robust inference in single firm/single event analyses," Journal of Corporate Finance, Elsevier, vol. 80(C).
    13. Brown, Stephen J. & Warner, Jerold B., 1985. "Using daily stock returns : The case of event studies," Journal of Financial Economics, Elsevier, vol. 14(1), pages 3-31, March.
    14. Zhong, Zhiyuan & Wu, Qiang & Wang, Manling, 2024. "Does the U.S.-China trade war stop? A novel event study on fake news and stock price in China," Finance Research Letters, Elsevier, vol. 66(C).
    15. Talwar, Shalini & Dhir, Amandeep & Kaur, Puneet & Zafar, Nida & Alrasheedy, Melfi, 2019. "Why do people share fake news? Associations between the dark side of social media use and fake news sharing behavior," Journal of Retailing and Consumer Services, Elsevier, vol. 51(C), pages 72-82.
    16. Bryan Fong, 2021. "Analysing the behavioural finance impact of 'fake news' phenomena on financial markets: a representative agent model and empirical validation," Financial Innovation, Springer;Southwestern University of Finance and Economics, vol. 7(1), pages 1-30, December.
    17. Shimon Kogan & Tobias J Moskowitz & Marina Niessner, 2023. "Social Media and Financial News Manipulation," Review of Finance, European Finance Association, vol. 27(4), pages 1229-1268.
    18. A. Craig MacKinlay, 1997. "Event Studies in Economics and Finance," Journal of Economic Literature, American Economic Association, vol. 35(1), pages 13-39, March.
    19. Eska, Fabian E. & Shi, Yanghua & Theissen, Erik & Uhrig-Homburg, Marliese, 2024. "Do design features explain the volatility of cryptocurrencies?," Finance Research Letters, Elsevier, vol. 66(C).
    20. Ralf Elsas & Daniela S. Schoch, 2023. "Robust inference in single firm/single event analyses," Post-Print hal-04325672, HAL.
    Full references (including those not matched with items on IDEAS)

    Most related items

    These are the items that most often cite the same works as this one and are cited by the same works as this one.
    1. Chia-Lin Chang & Shu-Han Hsu & Michael McAleer, 2018. "An Event Study Analysis of Political Events, Disasters, and Accidents for Chinese Tourists to Taiwan," Sustainability, MDPI, vol. 10(11), pages 1-77, November.
    2. Chang, C-L. & Hsu, S.-H. & McAleer, M.J., 2018. "An Event Study of Chinese Tourists to Taiwan," Econometric Institute Research Papers 2018-003/III, Erasmus University Rotterdam, Erasmus School of Economics (ESE), Econometric Institute.
    3. Ercan Balaban & Charalambos Th. Constantinou, 2006. "Volatility clustering and event-induced volatility: Evidence from UK mergers and acquisitions," The European Journal of Finance, Taylor & Francis Journals, vol. 12(5), pages 449-453.
    4. Imdat Dogan, "undated". "Testing The Merger Premiums In Publicly Traded Firms: The Case Of U.S. Commercial Banks," Review of Socio - Economic Perspectives 201831, Reviewsep.
    5. Pushpanjali Kaul & Sangeeta Arora, 2022. "Reinventing a brand’s identity: effect of name and logo announcements on the stock price of Indian banks," Journal of Brand Management, Palgrave Macmillan, vol. 29(3), pages 258-270, May.
    6. Cunha, P.A.M.F.V., 2005. "The value of cooperation : Studies on the performance outcomes of interorganizational alliances," Other publications TiSEM 59466e6c-1920-461e-b5e9-b, Tilburg University, School of Economics and Management.
    7. Corrado, Charles J. & Truong, Cameron, 2008. "Conducting event studies with Asia-Pacific security market data," Pacific-Basin Finance Journal, Elsevier, vol. 16(5), pages 493-521, November.
    8. Al-Ississ Mohamad, 2015. "The Cross-Border Impact of Political Violence," Peace Economics, Peace Science, and Public Policy, De Gruyter, vol. 21(2), pages 239-272, April.
    9. Henryk Gurgul & Pawel Majdosz & Roland Mestel, 2007. "Zur Verwendung von Regressionsmodellen im Rahmen von finanzwirtschaftlichen Ereignisstudien," Managerial Economics, AGH University of Science and Technology, Faculty of Management, vol. 1, pages 121-142.
    10. Pham, Thi Hong Hanh, 2015. "Energy management systems and market value: Is there a link?," Economic Modelling, Elsevier, vol. 46(C), pages 70-78.
    11. Walter, Andreas & Eisele, Florian, 2003. "Kurswertreaktionen auf die Ankündigung von Going Private : Transaktionen am deutschen Kapitalmarkt," Tübinger Diskussionsbeiträge 274, University of Tübingen, School of Business and Economics.
    12. Bayly, Nicholas & Breunig, Robert & Wokker, Chris, 2023. "Female Board Representation and Corporate Performance: A Review and New Estimates for Australia," IZA Discussion Papers 16617, Institute of Labor Economics (IZA).
    13. Elsas, Ralf & Schoch, Daniela Stephanie, 2023. "Robust inference in single firm/single event analyses," Journal of Corporate Finance, Elsevier, vol. 80(C).
    14. Maul, D. & Schiereck, D., 2017. "The bond event study methodology since 1974," Publications of Darmstadt Technical University, Institute for Business Studies (BWL) 80723, Darmstadt Technical University, Department of Business Administration, Economics and Law, Institute for Business Studies (BWL).
    15. Luca Aguzzoni & Gregor Langus & Massimo Motta, 2013. "The Effect of EU Antitrust Investigations and Fines on a Firm's Valuation," Journal of Industrial Economics, Wiley Blackwell, vol. 61(2), pages 290-338, June.
    16. Ma, Richie Ruchuan & Xiong, Tao & Bao, Yukun, 2021. "The Russia-Saudi Arabia oil price war during the COVID-19 pandemic," Energy Economics, Elsevier, vol. 102(C).
    17. Gokhale, Jayendra & Brooks, Raymond M. & Tremblay, Victor J., 2014. "The effect on stockholder wealth of product recalls and government action: The case of Toyota's accelerator pedal recall," The Quarterly Review of Economics and Finance, Elsevier, vol. 54(4), pages 521-528.
    18. Sebastien Bradley & Estelle Dauchy & Makoto Hasegawa, 2018. "Investor valuations of Japan’s adoption of a territorial tax regime: quantifying the direct and competitive effects of international tax reform," International Tax and Public Finance, Springer;International Institute of Public Finance, vol. 25(3), pages 581-630, June.
    19. Mateev, Miroslav & Andonov, Kristiyan, 2018. "Do European bidders pay more in cross-border than in domestic acquisitions? New evidence from Continental Europe and the UK," Research in International Business and Finance, Elsevier, vol. 45(C), pages 529-556.
    20. Atkas, Nihat & Bodt, Eric de & Roll, Richard, 2001. "Market Response to European Regulation," University of California at Los Angeles, Anderson Graduate School of Management qt0qc9p8gf, Anderson Graduate School of Management, UCLA.

    More about this item

    Keywords

    ;
    ;
    ;
    ;
    ;
    ;
    ;

    JEL classification:

    • G14 - Financial Economics - - General Financial Markets - - - Information and Market Efficiency; Event Studies; Insider Trading
    • L13 - Industrial Organization - - Market Structure, Firm Strategy, and Market Performance - - - Oligopoly and Other Imperfect Markets
    • G12 - Financial Economics - - General Financial Markets - - - Asset Pricing; Trading Volume; Bond Interest Rates
    • D83 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Search; Learning; Information and Knowledge; Communication; Belief; Unawareness

    Statistics

    Access and download statistics

    Corrections

    All material on this site has been provided by the respective publishers and authors. You can help correct errors and omissions. When requesting a correction, please mention this item's handle: RePEc:eee:finlet:v:73:y:2025:i:c:s1544612324016738. See general information about how to correct material in RePEc.

    If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

    If CitEc recognized a bibliographic reference but did not link an item in RePEc to it, you can help with this form .

    If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your RePEc Author Service profile, as there may be some citations waiting for confirmation.

    For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: Catherine Liu (email available below). General contact details of provider: http://www.elsevier.com/locate/frl .

    Please note that corrections may take a couple of weeks to filter through the various RePEc services.

    IDEAS is a RePEc service. RePEc uses bibliographic data supplied by the respective publishers.