KEIO RESEARCHERS INFORMATION SYSTEM

Profile 【 Display / hide 】

Profile 【 Display / hide 】

• From a time when mechanism design had almost no public recognition in Japan, I have worked not only on specialist academic papers, but also on bringing the field to a broader audience by writing books at every level—from introductory paperbacks and general-interest books to textbooks—while also promoting it through a wide range of media.
  
  Since the 2010s, I have focused on the practical business implementation of economics. In 2018, I founded what is now Toyotaka Sakai Office, and in 2020 I founded Economics Design Inc. My activities span a wide range, including the design of rules and algorithms, as well as angel investing accompanied by hands-on support.
  
  My mission is not only to produce academic knowledge, but to build the entire process through which that knowledge is ultimately put to use by ordinary people in society.

Academic Background 【 Display / hide 】

Academic Background 【 Display / hide 】

• 1998.03

  Waseda University, Faculty of Commerce

  University, Graduated

• 2005.05

  University of Rochester, Department of Economics

  United States, Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide 】

Academic Degrees 【 Display / hide 】

• Master, Kobe University, Coursework, 2000.03

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

• Humanities & Social Sciences / Economic theory (Theoritical Economics)

Papers 【 Display / hide 】

Papers 【 Display / hide 】

• The probability smoothing problem: Characterizations of the Laplace method

  Sakai T.

  Mathematical Social Sciences 135 2025.05

  ISSN  01654896

  　View Summary

  We formulate an axiomatic model to analyze the problem of probability smoothing in Naïve Bayes. We define several desirable properties of smoothing methods. Our main result shows that the Laplace smoothing method is the only one that satisfies ratio preservation, order preservation, and positivity. An alternative characterization based on reallocation-proofness is also obtained.

  • Access to Document (DOI)

• Preference manipulations lead to the uniform rule

  Bochet O., Sakai T., Thomson W.

  Journal of Economic Theory 220 2024.09

  ISSN  00220531

  　View Summary

  For the problem of fully allocating a social endowment of a commodity among a group of agents with single-peaked preferences, we study the consequences of manipulation for several families of rules that are not strategy-proof. Given a rule and a true preference profile, we consider the induced direct revelation game, and characterize its equilibrium allocations in terms of the profile. Our results are unequivocal: for any rule we consider, and for each true preference profile, there is a unique Nash equilibrium allocation. For the profile, it is the allocation of the uniform rule (Sprumont, 1991), the unique strategy-proof, efficient, and symmetric rule in this literature. These conclusions are drawn from two distinct sets of assumptions on the rules.

  • Access to Document (DOI)

• The net effect of advice on strategy-proof mechanisms: an experiment for the Vickrey auction

  Masuda T., Mikami R., Sakai T., Serizawa S., Wakayama T.

  Experimental Economics 25 ( 3 ) 902 - 941 2022.06

  ISSN  13864157

  　View Summary

  We conduct laboratory experiments for the multi-unit Vickrey auction with and without advice to subjects on strategy-proofness. The rate of truth-telling among the subjects without advice stays at 20%, whereas the rate increases to 47% among those who have received advice. By conducting similar experiments for the pay-your-bid auction, which is not strategy-proof, we confirm that the increase in truth-telling is due significantly to the net advice effect (i.e., the effect beyond the so-called experimenter demand effect). Moreover, we find that providing advice improves efficiency in the Vickrey auction, particularly in the early periods, when the subjects are less experienced. In general, subjects tend to overbid in Vickrey auction experiments. Our results indicate the possibility that providing simple advice decreases such overbidding by promoting a better understanding of the strategy-proofness of the Vickrey auction. Strategy-proof mechanisms are sometimes criticized because players often fail to recognize the benefit of telling the truth. However, our observations show that introducing advice on the property of strategy-proofness helps them behave “correctly.”

  • Access to Document (DOI)

Papers, etc., Registered in KOARA 【 Display / hide 】

Papers, etc., Registered in KOARA 【 Display / hide 】

• A search for the general will in a spatial model

  Sakai, Toyotaka

  Mita journal of economics (慶應義塾経済学会)  109 ( 4 ) 601(47) - 613(59) 2017.01

  ISSN  00266760

• Normative economics from the traditional and nontraditional views : preface

  Sakai, Toyotaka

  Mita journal of economics (慶應義塾経済学会)  109 ( 4 ) 555(1) - 556(2) 2017.01

  ISSN  00266760

• Designing practical mechanisms for indivisible good allocation

  Sakai, Toyotaka

  科学研究費補助金研究成果報告書 2011

• An axiomatic analysis to the NIMBY problem

  Sakai, Toyotaka

  Keio journal of economics (慶應義塾経済学会)  100 ( 4 ) 941(57) - 949(65) 2008.01

  ISSN  00266760

Reviews, Commentaries, etc. 【 Display / hide 】

Reviews, Commentaries, etc. 【 Display / hide 】

• Correction to: The net effect of advice on strategy-proof mechanisms: an experiment for the Vickrey auction (Experimental Economics, (2022), 25, 3, (902-941), 10.1007/s10683-021-09736-5)

  Masuda T., Mikami R., Sakai T., Serizawa S., Wakayama T.

  Experimental Economics 26 ( 1 ) 249 - 250 2023.03

  ISSN  13864157

  　View Summary

  Incorrect version of the ESM was mistakenly uploaded during proofing. The original article has been corrected.

  • Access to Document (DOI)

Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• SEMINAR: MICROECONOMICS

  2026

• TOPICS IN MICROECONOMICS

  2026

• RESEARCH SEMINAR B

  2026

• MICROECONOMICS

  2026

• RESEARCH SEMINAR D

  2026

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