Curriculum Vitaes

Isaka Naoto

  (井坂 直人)

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Professor, Faculty of Liberal Arts, Department of Liberal Arts, Sophia University
Bachelor of Arts in Foreign Studies(Sophia University)
Master of Arts in International Public Policy(Osaka University)
Doctor of Philosophy in Economics(Hitotsubashi University)

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  • Naoto Isaka
    Gendai Finance, 44 19-55, Feb 15, 2022  Peer-reviewedLead authorCorresponding author
  • Naoto Isaka
    PACIFIC-BASIN FINANCE JOURNAL, 46 191-211, Dec, 2017  Peer-reviewedLead authorCorresponding author
    In this study, I analyze the optimal choice of a board of directors using a theoretical model. In my model, shareholders choose either an informed board that can bring additional private information to the firm or an uninformed board that merely considers the inside information already available within the firm. Then, the board randomly chooses a good chief executive officer (CEO) who has inside information or a bad CEO without such information. Next, the CEO decides whether to consult with the board when making a project decision. I show that shareholders generally choose an informed board in order to maximize the firm's value by utilizing the private information available to the board. However, shareholders optimally select an uninformed board if the CEO is reluctant to communicate with an informed board out of fear that it will reject his/her decisions. The uninformed board is also optimal when it derives a sufficiently large private benefit from monitoring the CEO, the cost of choosing the informed board is large, or the firm is involved in many unrelated businesses, especially when the inside information is valuable and many outsiders are needed to observe useful outside information. Some of these implications are used to discuss recent trends in the board structures of Japanese firms.
  • Naoto Isaka
    INTERNATIONAL REVIEW OF FINANCE, 14(1) 75-103, Mar, 2014  Peer-reviewed
    Abstract We examine empirically the long-run effects of reductions in minimum trading units (MTU) on stock prices in Japan from October 2001 to May 2008. When firms reduce their MTU, the number of individual shareholders tends to increase significantly for several years. We estimate buy-and-hold abnormal returns and find that positive stock returns are observed not only for the period between the announcement day and the actual date of MTU decreases, but also for a period of several years following MTU reductions. In addition, we measure stock price reactions to the release of public information before and after MTU reductions and find that stock prices react less to the release of positive information and more to the release of negative information after the MTU reductions. These findings, together with evidence of the change in the short and long positions of investors after the MTU reductions, indicate that individual investors face short-sales constraints.
  • ISAKA NAOTO, Hiroshi Yoshikawa
    Financial Decisions, 25(2) 1-20, Dec, 2013  Peer-reviewed
  • Naoto Isaka
    Sophia-R, 1-23, Mar, 2012  



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