Researcher Database
Last Updated :2024/07/25
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Profile and Settings
Name (Japanese)
HayakawaName (Kana)
HitoshiName
201501036141964976
Alternate Names
Achievement
Research Interests
Research Areas
Research Experience
- 2019/04 - Today Hokkaido University Faculty of Economics and Business Associate professor
- 2015/02 - 2019/03 Hokkaido University Creative Research Institution (Faculty of Economics and Business) Assistant professor
- 2013/04 - 2015/02 The University of Tokyo Graduate school of Economics Assistant professor
Published Papers
- Naoshi Doi, Hitoshi HayakawaINTERNATIONAL JOURNAL OF THE ECONOMICS OF BUSINESS 27 (2) 303 - 320 1357-1516 2020/05 [Refereed]
This paper reviews existing studies investigating online communication on products and services, also known as, electronic word-of-mouth (eWOM). The first half of the paper summaries what is known about eWOM in the literature. Existing studies largely relate to the marketing field and are generally conducted from a marketing firms' point of view. To investigate eWOM from the perspective of social welfare, the latter half of the paper discusses theoretical frameworks of economics that are potentially applicable to the context of eWOM, especially focusing on theories about social learning and signaling. We discuss implications obtained by applying these theories to eWOM and outline possible directions for future research. - Hitoshi HayakawaCOMPUTATIONAL ECONOMICS 55 (1) 253 - 301 0927-7099 2020/01 [Refereed][Not invited]
This study investigates the amount of liquidity that is necessary to settle a given network of financial obligations. In our analysis, we assume sequential settlement, which is standard in real-world interbank settlement systems, instead of simultaneous settlement, which is typically assumed in relevant research. We develop a graph-theoretic model and apply a flow network technique to investigate how the interconnected feature could affect the required liquidity. Our main contribution is to show that the effect of the interconnected feature is characterized with our original concepts regarding "twist" properties-arc-twisted and vertex-twisted-that are defined on the basis of the concept of "cycles." Each of the "twist" properties refers to certain inconsistency in the dynamics of settlements. The characterization provides a consistent and fundamental perspective of how a hub or other network structures affect the required liquidity. We further investigate the quantitative implications of the "twist" properties for real-world networks of obligations by examining networks with clustered structures and small-world structures. We show that "twist" properties have non-linear effects on the required liquidity against an increase in the amount of obligations. - Hitoshi Hayakawa, Toshimasa Ishii, Hirotaka Ono, Yushi UnoDISCRETE APPLIED MATHEMATICS 265 86 - 103 0166-218X 2019/07 [Refereed][Not invited]
In the economic activities, the central bank has an important role to cover payments of banks, when they are short of funds to clear their debts. For this purpose, the central bank timely puts funds so that the economic activities go smooth. Since payments in this mechanism are processed sequentially, the total amount of funds put by the central bank critically depends on the order of the payments. Then an interest goes to the amount to prepare if the order of the payments can be controlled by the central bank, or if it is determined under the worst case scenario. This motivates us to introduce a brand-new problem, which we call the settlement fund circulation problem. The problems are formulated as follows: Let G = (V, A) be a directed multigraph with a vertex set V and an arc set A. Each arc a is an element of A is endowed debt d(a) >= 0, and the debts are settled sequentially under a sequence pi of arcs. Each vertex V is an element of V is put fund in the amount of p(pi)(v) >= 0 under the sequence. The minimum maximum settlement fund circulation problem (MIN-SFC/MAx-SFC) in a given graph G with debts d : A -> R+ U {0} asks to find a bijection pi : A -> {1,2, ..., vertical bar A vertical bar} that minimizes/maximizes the total funds Sigma(v is an element of V) P-pi(v). In this paper, we show that both MIN-SFC and MAX-SFC are NP-hard; in particular, MIN-SFC is (I) strongly NP-hard even if G is (i) a multigraph with vertical bar V vertical bar = 2 or (ii) a simple graph with treewidth at most two, and is (II) (not necessarily strongly) NP-hard for simple trees of diameter four, while it is solvable in polynomial time for stars. Also, we identify several polynomial time solvable cases for both problems. (C) 2019 Elsevier B.V. All rights reserved. - Hitoshi Hayakawa, Susumu Imai, Kazuko NakataJAPANESE ECONOMIC REVIEW 69 (3) 324 - 339 1352-4739 2018/09 [Refereed]
In this paper, we survey the empirical analysis of brands. The difficulty in this area of research is that even though a brand is easily identifiable, its economic roles are not directly observable. We first discuss methods where the effect of a brand is measured as the unobservable component of sales or price of a product, which researchers recover as a residual of the sales or price regression. We then describe the approaches to estimate the various roles of brands, such as providing information and increasing the utility of consumption. Finally, we provide examples of research that highlight the role of brands in exploiting the irrationality of consumers for profit. - Hitoshi HayakawaJOURNAL OF ECONOMIC INTERACTION AND COORDINATION 13 (1) 9 - 50 1860-711X 2018/04 [Refereed][Not invited]
This study investigates whether and how central clearing influences the overall liquidity needs in a network of financial obligations. Utilizing the approach of flow network theory, we show that the effect of adding a central clearing counterparty (CCP) is decomposed into two effects: central routing, and central netting effects. Each effect can produce different liquidity needs according to different liquidity scenarios. The analysis indicates that adding a CCP in times of financial distress successfully reduces the overall liquidity needs if and only if the netting efficiency of the CCP is sufficiently high. Furthermore, once the economy is no longer in financial distress, higher netting efficiency of the CCP could conversely increase the overall liquidity needs. The results have implications for the effectiveness of CCPs in mitigating systemic risk in times of financial distress, and their operating costs once the distress has passed. - Hitoshi Hayakawa, Toshimasa Ishii, Hirotaka Ono, Yushi UnoLeibniz International Proceedings in Informatics, LIPIcs 92 1868-8969 2017/12/01 [Refereed][Not invited]
In the economic activities, the central bank has an important role to cover payments of banks, when they are short of funds to clear their debts. For this purpose, the central bank timely puts funds so that the economic activities go smooth. Since payments in this mechanism are processed sequentially, the total amount of funds put by the central bank critically depends on the order of the payments. Then an interest goes to the amount to prepare if the order of the payments can be controlled by the central bank, or if it is determined under the worst case scenario. This motivates us to introduce a brand-new problem, which we call the settlement fund circulation problem. The problems are formulated as follows: Let G = (V,A) be a directed multigraph with a vertex set V and an arc set A. Each arc a 2 A is endowed debt d(a) 0, and the debts are settled sequentially under a sequence of arcs. Each vertex v 2 V is put fund in the amount of p(v) 0 under the sequence. The minimum/maximum settlement fund circulation problem (Min-SFC/Max-SFC) in a given graph G with debts d : A ! R+ [ {0} asks to find a bijection : A {1, 2,. . . , |A|} that minimizes/maximizes the total funds P v2V p(v). In this paper, we show that both Min-SFC and Max-SFC are NP-hard in particular, Min-SFC is (I) strongly NP-hard even if G is (i) a multigraph with |V | = 2 or (ii) a simple graph with treewidth at most two, and is (II) (not necessarily strongly) NP-hard for simple trees of diameter four, while it is solvable in polynomial time for stars. Also, we identify several polynomial time solvable cases for both problems.
Research Projects
- Japan Society for the Promotion of Science：Grants-in-Aid for Scientific ResearchDate (from‐to) : 2024/04 -2028/03Author : 松島 斉, 釜賀 浩平, 矢ヶ崎 将之, 日引 聡, 佐野 隆司, 星 岳雄, 早川 仁, 野田 俊也, 岡崎 哲二
- Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)Date (from‐to) : 2020/04 -2024/03Author : 松島 斉, 尾山 大輔, 萱場 豊, 山本 裕一, 佐野 隆司, 中島 大輔, 安田 洋祐, 早川 仁, 岡崎 哲二成果は１０テーマについてであり、学術貢献とメディア情報発信をおこなった。１．ブロックチェーンとガバナンス：松島と野田は、ブロックチェーンの普及が実体経済にどのような影響を与えるかを明らかにする論文を完成させ、東大広報などを通じて海外に向けてプレスリリースし、大きな反響を得た。２．ブロックチェーンと情報デザイン：山本は、不確実性下において不適切に特定化されたモデルにもとづいた意思決定がもたらす経済学的帰結についての論文を専門誌に掲載させた。３．繰り返しゲームと信用：松島と萱場は、繰り返しゲームの理論研究を完成させ、専門誌に掲載させた。４．プライバシーと制度設計：松島は、不確実性下において、適切な資源配分が可能になるインセンティブメカニズムを、向社会的動機を利用することを前提として設計できることを示す論文を完成させた。５．限定合理性とインセンティブ：中島は、限定合理的な意思決定者による意思決定バイアスについての理論的基礎をつくる論文を専門誌に掲載させた。松島は、前川と矢ヶ崎との共同で、取引市場におけるフレーミングの重要性についての実験と理論の研究を進展させた。６．動学的オークションと５G：佐野は、動学的オークションのおける割引率の異質性についての理論的基礎を構築し、専門誌に掲載させた。７．自動化と日本経済史：岡崎は、明治以降の日本の産業化における技術革新と製品多角化、企業成長についての歴史的考察をまとめ、専門誌に掲載させた。尾山は、人口移動の動学的モデルをインセンティブの視点から分析し、地域間の人口分布格差を説明する論文を専門誌に掲載させた。８．倫理的社会選択：松島は、社会選択を、個人の選好の集計ではなく、異なる倫理的基準の妥協案として、公理論的に解明する論文を完成させた。１０．グローバルコモンズ：松島は、温暖化交渉の制度設計を考えるための基礎理論をスタートさせた。
- 日本学術振興会：科学研究費助成事業 若手研究Date (from‐to) : 2020/04 -2024/03Author : 早川 仁本研究の中心的課題である、貨幣的一般均衡モデルの構築ならびにそこでの資産バブルの分析に関して、ワーキングペーパーにまとめた。論文においては、貨幣供給量の拡大の経済成長における意義を示すとともに、過剰な貨幣供給のもとで資産バブルがもたらされうることを示すことに成功した。従来の研究において、非貨幣的一般均衡モデルにおける資産バブルの発生・厚生への影響については種々の知見が得られているが、当論文で示した資産バブルはそれらとは本質的に異なる種類の資産バブルと位置づけられる。非貨幣的一般均衡モデルにおいて資産バブルの発生の根拠は経済活動の制約や摩擦であり、その発生の厚生上の一義的効果は制約や摩擦を緩和することを通じた正の効果として把握される一方、当論文においては資産バブルの発生の根拠は貨幣の偏在として観察される所得・資産の不平等に求められ、かつ、資産バブルの発生はその不平等を拡大する傾向にあることが示される。当論文は、非貨幣的モデルにおける資産バブルの分析に関して、現実の資産バブルを適切に理解できていない可能性を示唆する。 当論文はまた、資産バブルの代替的動学として、所得・消費の格差の拡大を必然的にともなう生産セクター間の生産要素のシフトを示す。すなわち、貨幣の過剰が生じている際、もし新たな生産セクターがすぐには稼働できない場合、過剰な貨幣が資産市場に流入することによって資産バブルが発生しうる。一方、新たな生産セクターへの貨幣の流入は生産要素のシフトを生じ、その時点での富裕層を利する一方、他の家計の損失を必然的にともなうことが示される。いずれの動学においても貨幣の偏在がさらなる格差の拡大をもたらすことが示される。