Authorship：Coinvestigator(s) 

We develop a new method to identify bid rigging in government procurement auctions and obtain a large number of samples of cartels that has not been subject to legal auction. Using these samples, we conduct hypothesis testing to examine the mechanisms of cartel formation, maintenance, and breakdown within a repeated game framework and provide empirical evidence that communication among cartel members plays a critical role in sustaining collusion. We also apply the detection method to data from developing countries and document the presence of collusion.

Authorship：Coinvestigator(s) 

2010年のノーベル経済学賞の対象となった「サーチ理論」は、微小な粒子同士のランダムなぶつかり合いとして経済活動を再定義することで市場の「摩擦」をモデル化することに成功した。しかしながら、「微小な経済主体」という世界観は分析上の制約になることも多かった。本研究は、「企業規模」という概念をモデル化することを通じてサーチ理論を大きく発展させ、世界規模で進む市場構造の変質、特に近年報告されている市場支配力の上昇や労働分配率の下落などの現象を、産業組織、景気変動に伴う雇用調整、所得分布の視点から解明する。
プロジェクト１：摩擦的市場における企業規模　本プロジェクトは、研究代表者が長年研究してきた「サーチ理論」を「産業組織論」に応用するという方法を採用し、産業組織論をサーチ理論を通じて再構築するプロジェクトである。研究分担者との共同研究の成果を「Priminence and Market Power: Asymmetric Oligopoly with Sequential Consumer Search」という論文にまとめ、現在国際ジャーナルにて２回目の書き換え要求に対応し終え、最終的な審査結果を待っている状態である。
プロジェクト２：摩擦的市場と景気変動　研究代表者と研究分担者による共同研究の成果のひとつ「General Equilibrium Effects and Labor Market Fluctuations」では、景気変動における「所得効果」の役割について数量分析を行い、Economic Modellingという国際専門誌に掲載された。また、「Time Aggregation and Unemployment Volatility」では、労働市場統計の集計上のバイアスが景気変動を過小に計測してしまう可能性についてシミュレーションによって明らかにし、Economics Bulletinという国際専門誌に掲載が決まった。「Robots and Unemployment」では、技術進歩によって雇用が失われる可能性について理論分析と数量分析を行った。当該年度中に複数の専門誌にて審査を受け、まだ掲載は決まっていないものの、審査から得られたコメント等を元に、分析結果の中身を精査し、研究の新規性を打ち出すにはどうするか、新しい方向性を発見するに至った。
プロジェクト１の研究成果である論文「Priminence and Market Power: Asymmetric Oligopoly with Sequential Consumer Search」が経済学分野で伝統のある学術誌の審査に残っており、２度の書き換え作業を経て、２３年度中には掲載が決まると見込まれる。この研究成果を土台として次の研究に進むことが可能になる。プロジェクト２についてもすでに専門誌に２本掲載が決まっており、残りの研究期間を使って他の現在進行中の研究を完了させることができる見通しになったから。
プロジェクト１「摩擦的市場における企業規模」については、引き続き花薗教授との共同研究を推進し、市場の摩擦と市場支配力の推移について分析を進め、ますます加速してゆく情報化社会の中で少数の企業が巨大化していくのか、それとも多数の企業による競争的な市場に向かっていくのかについて解明を進める計画である。プロジェクト２「摩擦的市場と景気変動」についても引き続き宮本教授と研究を進め、当該年度までに複数の方向で数理モデル構築とシミュレーションが進んでいる研究成果について、次年度中にそれぞれ論文にまとめていくことを目標としている。

Authorship：Coinvestigator(s) 

In this study, we conducted a seeds research on economic analysis related to sake　(Sakenomikusu). In the research, interviews provided suggestions on the relationship between the efficiency of sake producers and exports and differentiation. In the empirical study, retail data was used to provide suggestions on seasonal changes in consumer behavior and substitutability with other alcoholic beverages. In the theoretical analysis, we applied an economic model in which large companies and small companies coexist, and clarified the impact of changes in demand for sake.

Authorship：Coinvestigator(s) 

We contributed to the development of basic and applied research in the field of contract theory and organizational economics, and the formation of inter-university research network at the level of the international standard, through the following workshops, conferences, and academic presentations and publications: (1) Regular monthly workshops (CTW); (2) Summer conferences held every August (not held in person due to COVID-19 for 2020-2022); (3) International theory conferences joint with scholars in Taiwan, Hong Kong, Korea, and other Asian and Pacific nations held every December (not held due to COVID-19 for 2020-2022); (4) Other conferences and workshops; and (5) Academic presentations and interactions at domestic and international conferences and academic publications.

Authorship：Principal investigator 

Grant amount：\11050000 （ Direct Cost: \8500000 、 Indirect Cost：\2550000 ）

We show that in procurement auctions, providing stronger incentives to exert effort backfires due to incomplete monitoring and fear of bankruptcy: it leads to adverse selection in auctions where financially weaker firms that are more likely to bankrupt tend to win. Moreover the cost efficiency deteriorates as well. We also work on the foundation of scoring auctions and establish a theory and a methodology for structural estimation, allowing general scoring rule and multidimensional type space.

Authorship：Coinvestigator(s) 

In practice, many contracts are piecewise-linear. An important aspect of this research is the complexity of contracts. The objectives of this study are to (1) examine whether simple piecewise-linear contracts perform well relative to fine-tuned optimal contracts in principal-agent settings, and (2) investigate the effects of non-uniform heterogeneity across agents and/or psychological aspects of decision making such as counterfactual thinking and epsilon-contamination.
Regarding the validity of simple contracts, for example, it turns out that a properly designed simple quota-based piecewise-linear contract performs well on the entire region of the relevant parameter values in a principal-agent problem under moral hazard and adverse selection.

Authorship：Principal investigator 

Grant amount：\14430000 （ Direct Cost: \11100000 、 Indirect Cost：\3330000 ）

First, we establish some foundations of the analysis of auctions and contracts in public procurement, contributing to our understanding of bidder behavior and desirable institutional design. In particular, we find a workable model to study bidder behavior in general scoring auctions, derive optimal scoring rule when the quality is multidimensional, and also establish a method to detect bidder collusion from large scale auction data.
Second, we find how procurement design affects the performance. In particular, we empirically analyze the effect of bundling in procurement, and theoretically discover how bidder incentive changes in simultaneous or sequential multi-unit auctions.

Authorship：Principal investigator 

Grant amount：\3120000 （ Direct Cost: \2400000 、 Indirect Cost：\720000 ）

We build models of scoring auctions and obtain the following highly useful results. First, we consider a symmetric auction in which bidder's private information is multidimensional, and derive a condition under which an equilibrium of the bidding game exists. The condition is that the dimensions of private information that influence fixed costs of each bidder is perpendicular to those that affect variable costs. Second, we study the effects of bid restrictions such as price upper-bound or quality bounds in the model of single-dimensional private information. We show that the analysis is basically the same as in the model without restrictions unless the multiple inequality restrictions bind at the same time.

Authorship：Coinvestigator(s) 

We contributed to the development of basic and applied research in the field of contract theory and organizational economics (2016 Nobel Prize in Economic Sciences was awarded to two contributors in this field) and the formation of inter-university research network at the level of the international standard, through the following workshops, conferences, and academic presentations: (1) Regular forty workshops (CTW) during the five years, including sixteen talks by researchers from abroad; (2) Summer conferences held every August; (3) International conferences joint with Taiwan, Hong Kong, and other Asian and Pacific nations held every December; (4) Workshops (CTWE) held in Tokyo, including twelve talks by researchers from abroad; and (5) Forty-seven academic presentations and interactions at domestic and international conferences and thirty-one academic articles.

Authorship：Principal investigator