基本情報

所属

• 経済学研究院　現代経済経営部門　経済政策分野

職名

• 准教授

学位

• 博士(経済学)（東京大学）

ホームページURL

https://sites.google.com/view/hitoshihayakawa/ホーム
https://sites.google.com/view/hitoshihayakawa/home

J-Global ID

• 201501036141964976

研究キーワード

• 決済システム   金融ネットワーク   資産バブル   貨幣経済   

研究分野

• 人文・社会 / 経済政策

職歴

• 2019年04月 - 現在 北海道大学 経済学研究院 准教授
• 2015年02月 - 2019年03月 北海道大学 創成研究機構 (経済学研究院） 特任助教
• 2013年04月 - 2015年02月 東京大学 経済学研究科 助教

研究活動情報

論文

• Electronic word-of-mouth: a survey from an economics perspective

  Naoshi Doi, Hitoshi Hayakawa

  INTERNATIONAL JOURNAL OF THE ECONOMICS OF BUSINESS 27 2 303 - 320 2020年05月 [査読有り]
   

  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.
• Liquidity in Financial Networks

  Hitoshi Hayakawa

  COMPUTATIONAL ECONOMICS 55 1 253 - 301 2020年01月 [査読有り][通常論文]
   

  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.
• Settlement fund circulation problem

  Hitoshi Hayakawa, Toshimasa Ishii, Hirotaka Ono, Yushi Uno

  DISCRETE APPLIED MATHEMATICS 265 86 - 103 2019年07月 [査読有り][通常論文]
   

  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.
• Empirical Analysis of Brands: A Survey

  Hitoshi Hayakawa, Susumu Imai, Kazuko Nakata

  JAPANESE ECONOMIC REVIEW 69 3 324 - 339 2018年09月 [査読有り]
   

  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.
• Does a central clearing counterparty reduce liquidity needs?

  Hitoshi Hayakawa

  JOURNAL OF ECONOMIC INTERACTION AND COORDINATION 13 1 9 - 50 2018年04月 [査読有り][通常論文]
   

  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.
• Settlement fund circulation problem

  Hitoshi Hayakawa, Toshimasa Ishii, Hirotaka Ono, Yushi Uno

  Leibniz International Proceedings in Informatics, LIPIcs 92 2017年12月01日 [査読有り][通常論文]
   

  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.

共同研究・競争的資金等の研究課題

• 近未来デジタル経済のための制度設計：理論、実証、実践

  日本学術振興会：科学研究費助成事業 基盤研究(A)

  研究期間 : 2020年04月 -2024年03月 

  代表者 : 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
• 貨幣的一般均衡モデルにおける資産バブルを中心とした分析

  日本学術振興会：科学研究費助成事業 若手研究

  研究期間 : 2020年04月 -2024年03月 

  代表者 : 早川 仁

教育活動情報

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