Optimal Dynamic Incentive Contracts between a Principal and Multiple Agents in Controlled Markov Processes: A Constructive Approach
Yasuaki Wasa, Ken-Ichi Akao, Kenko Uchida
RIEEM Discussion Paper Series
2001
1
-
18
2020.02
Incentive-based economic and physical integration for dynamic power networks
Yasuaki Wasa, Toshiyuki Murao, Ken Ichi Akao
Economically Enabled Energy Management: Interplay Between Control Engineering and Economics
181
-
211
2020.01
View Summary
This chapter describes an incentive-based market that integrates the economic layer and the physical layer to guarantee high-quality physical ancillary services in dynamic power networks. Toward the full liberalization of the electricity markets, it is indispensable to develop a socially optimal regulation market with a high-speed market-clearing mechanism while preventing maliciously strategic biddings of market participants called agents. To realize the markets, the utility functioning as a system operator prepares an appropriate incentive mechanism to elicit the agents’ private information. We refer to this real-time incentive-enabled market as an incentivizing market. After illustrating the issues of the agents’ strategic biddings without incentive mechanisms, we mainly propose incentivizing market mechanisms for moral hazard problems and adverse selection problems in dynamic power networks, respectively. We also discuss features, possibilities, and limitations of our proposed mechanisms through simulations for linear quadratic Gaussian (LQG) power networks.
RIEEM Discussion Paper Series
No.1905
1
-
26
2019.07
A theory of disasters and long-run growth
Ken-Ichi Akao, HIroaki Sakamoto
Journal of Economic Dynamics & Control
95
89
-
109
2018.10
[Refereed]
View Summary
This paper develops a unified framework in which various types of catastrophic shocks can be simultaneously considered within a standard model of economic growth. We first establish the basic existence and equivalence results. We then apply the framework to an endogenous growth model to consider the influence of disasters on the long-term equilibrium and the transition phase. The result shows that while experiencing disasters may lower the average growth rate of the affected countries, there exist various channels through which the risk of disasters and long-term economic performance are positively correlated. This finding reconciles the apparently contradictory evidence in recent empirical studies.
The Home Appliance Eco-Point System was a subsidy program implemented by the Japanese government from May 2009 to March 2011. The system has two features. First, the subsidy was provided in the form of eco-points that were only exchangeable for environmentally friendly goods. Second, it was a replacement subsidy program for durable goods with uncertain termination dates. We investigate the policy implications of these features. We show that if the eco-points are exchangeable for any goods (i.e., if a simple rebate program rather than an eco-point system is implemented), the same outcome can be achieved at a lower subsidy rate and thus using fewer financial resources. Regarding the eco-point system as a replacement subsidy, we show that the uncertain termination has the same effect as an increase in the subsidy: both accelerate the replacement. Uncertainty is a substitute for a subsidy, thus saving the financial resources of the government. However, there are two welfare concerns: (a) acceleration may not be desirable in terms of the environment, and (b) it costs households their expected utility.
JOURNAL OF ENERGY ENGINEERING
143
(
3
)
2017.06
[Refereed]
View Summary
In recent decades, climate change and resource limitations have become serious problems. To overcome these problems, many countries promote the introduction of renewable energy. However, the diffusion of renewable energy requires a novel supply and demand system for electricity. One remarkable method of controlling electricity demand is a demand-side control based on dynamic pricing. This study analyzes electricity consumption behavior using laboratory experiments. In particular, the authors focus on the effect of supply limitations on consumption behavior. The results of the experiment include significant findings that help provide an understanding of electricity consumption behavior. More specifically, the announcement of a supply limitation affects the decision to consume electricity. Results of this study indicate that cooperative people tend to decrease electricity consumption more when they are aware of the possibility of an electrical outage. This finding implies that researchers need a better understanding of the psychological aspects of electricity consumption behavior. (C) 2016 American Society of Civil Engineers.
Review of Environmental Economics and Policy Studies
9
(
2
)
1
-
20
2016
[Refereed]
View Summary
<p>This paper provides an overview of the standard theory of discounting in cost-benefit analysis. With an application to long-term environmental problems in mind, we begin with the classic issue of discounting and intergenerational equity, which dates back to the seminal work of Frank Ramsey in the 1920s. Then, by reviewing recent developments in the theory of declining discounting rates (DDRs), we show how relatively low and declining discount rates can be justified in the presence of uncertainty. Also, we briefly discuss the practical implications of discounting in the context of climate change.</p>
RIEB Discussion Paper Series
DP2015
(
39
)
1
-
37
2015.09
Determining future environmental value: Empirical analysis of discounting over time and distance
Tetsuya Tsurumi, Kei Kuramashi, Shunsuke Managi, Ken Ichi Akao
The Routledge Handbook of Environmental Economics in Asia
470
-
490
2015.01
View Summary
Economists have argued about various discount rates. Strotz (1955-56) first suggested that there is no reason to consider a time-consistent discount rate such as an exponential function. Over the past five decades, various functional theoretical forms have been proposed, including exponential, hyperbolic, and quasi-hyperbolic. Simultaneously, empirical studies have found there is a possibility that observed discount rates are not constant over time. The data tend to not fit exponential functional forms but rather hyperbolic ones; this implies declining discount rates. Furthermore, empirical studies have found that discount rates vary across objects. Fredrick et al. (2002) summarized the annual discount rates found in previous empirical studies. Table 23.1 summarizes annual discount rates estimated in previous literature. The literature suggests various annual discount rates, and the results depend on the type of goods, the time range, and/or the estimation methods. In this chapter, we consider the discount rates on environmental values, and especially on long-term problems, as these are not empirically addressed in previous literature.
We show that in poor resource-based communities, the socio-psychological preference for employment, which arises from a strong desire to follow the communal norm of sharing in harvesting efforts, can lead to the optimality of full-employment harvesting until resource extinction. We show that such communities may be able to sustain both their natural resources and full employment by using outside-the-community employment opportunities or by economic diversification. However, to be effective, such policies must ensure that the outside wage rate and the initial capital stock are above certain minimum levels which depend on the existing size of the resource stock, the characteristics of the community’s harvesting technology, and the biological growth characteristics of the resource in question, and which will be higher the longer the remedial policies are delayed.
This paper defines a sustainable development path as a balanced growth path with environmental conservation. In the framework of endogenous growth theory, it is known that a sustainable development path is optimal only if the following three conditions are satisfied: (1) the engine of economic growth is clean (2) the assimilation capacity of the environment is high enough to endure the increasing environmental load with economic growth and (3) the population has an egalitarian propensity with the elasticity of the marginal utility of consumption that is greater than or equal to one. While all of these three conditions are intuitively plausible, there are distinctions between the first two and the last one: the former can be obtained by our endeavors, whereas the latter concerns preference that is endowed rather than obtained. We show that this preference constraint can be relaxed if the production technology satisfies the condition that the elasticity of transformation to the production factor and the environmental service, after appropriate monotone transformation, is greater than one.
It is known that in an intertemporal competitive economy, a tradable permit system may not achieve efficiency without setting appropriate permit interest rates (i.e., rewards for holding permits). To find the rates, however, we need to know in advance the path of efficient permit prices, which is difficult to obtain. This study intends to solve this problem in two ways. First, we analyze a special case in which the permit interest rates are given by a simple rule. For example, if the marginal abatement cost of pollution emission is constant, then the appropriate rate is to equal the monetary interest rate. As is the case for global warming, if the damage is caused in the future far beyond the planning period of the environmental program, the appropriate rate coincides with the marginal self-recovery of environmental stock under certain conditions. As a second approach, we propose a tradable permit system with a permit bank, as a mechanism by which the permit interest rates are generated endogenously without governmental intervention other than the issuance of permits. However, we also show that this approach raises the problem of indeterminacy of the equilibrium.
RIETI Discussion Paper Series
13-E-061
1
-
39
2013.07
持続可能な発展は社会にとって望ましいことか?
赤尾健一
平成24年度ガス事業研究会報告書
2013.03
Some rationalizability results for dynamic games
Ken-Ichi Akao, Tapan Mitra, Gerhard Sorger
INTERNATIONAL JOURNAL OF ECONOMIC THEORY
8
(
4
)
361
-
379
2012.12
[Refereed]
View Summary
We study the relation between dynamical systems describing the equilibrium behavior in dynamic games and those resulting from (single-player) dynamic optimization problems. More specifically, we derive conditions under which the dynamics generated by a model in one of these two classes can be rationalized by a model from the other class. We study this question under different assumptions about which fundamentals (e.g. technology, utility functions and time-preference) should be preserved by the rationalization. One interesting result is that rationalizing the equilibrium dynamics of a symmetric dynamic game by a dynamic optimization problem that preserves the technology and the utility function requires a higher degree of impatience compared to that of the players in the game.
We show that the critical capital stock of the Dechert and Nishimura (1983) model is a decreasing and continuous function of the discount factor. We also show that the critical capital stock merges with a nonzero steady state as the discount factor decreases to a certain boundary value, and that the critical capital stock converges to the minimum sustainable capital stock as the discount factor increases to another boundary value. (C) 2011 Elsevier B.V. All rights reserved.
This paper evaluates tax schemes in a class of differential games. The results indicate that there are many tax schemes that support efficient resource usage, but each may fail to implement the targeted resource because of the multiplicity of equilibria. Since all of the equilibria are subgame perfect, it is difficult to predict which specific one arises. Care must then be taken in using a tax scheme as a remedy for the "tragedy of the commons." The advantages of other policy instruments (including command-and-control regulation and a tradable permit system) are also discussed.
Feasibility and optimality of sustainable growth under materials balance
Ken-Ichi Akao, Shunsuke Managi
JOURNAL OF ECONOMIC DYNAMICS & CONTROL
31
(
12
)
3778
-
3790
2007.12
[Refereed]
View Summary
Pollution from consumption and production is an inevitable part of economic processes. We employ a materials balance approach and develop an endogenous growth theory, with recycling activity, to examine the evolution of the economic and environment systems. This paper provides feasibility and optimality conditions for sustainable economic growth with rising environmental quality. The fundamental condition of feasibility is that the flow of natural resources, which eventually returns to the environment as waste and pollution, has a negative growth rate in the long run. (C)2007 Elsevier B.V. All rights reserved.
Exhaustion of a natural resource stock may be a rational choice for an individual and/or a community, even if a sustainable use for the resource is feasible and the resource users are farsighted and well informed on the ecosystem. We identify conditions under which it is optimal not to sustain resource use. These conditions concern the discounting of future benefits, instability of a social system or ecosystem, nonconvexity of natural growth function, socio-psychological value of employment, and strategic interaction among resource users. The identification of these conditions can help design policies to prevent unsustainable patterns of resource use.
Economic analysis of forest management with a long rotation period and a small labor input (I) Behavior of forest owners about an increase in real wage rates
Kenichi Akao
Journal of the Japanese Forest Society
73
(
6
)
419
-
425
1991.11
[Refereed]
Incentive-Based Economic and Physical Integration for Dynamic Power Networks (in Hatanaka, T., Y. Wasa, and K.Uchida (Eds.) Economically Enabled Energy Management: Interplay Between Control Engineering and Economics.)
Wasa, Y, T. Murao, K. Akao(
Part:
Contributor)
Springer
2020.05
Diversity Function (Society for Environmental Economics and Policy Studies ed. Handbook of Environmental Economics and Policy Studies)
Ken-Ichi Akao(
Part:
Contributor)
Maruzen
2018.05
ISBN:
9784621302927
The Tragedy of the Commons and Dynamic Game (Society for Environmental Economics and Policy Studies ed. Handbook of Environmental Economics and Policy Studies)
Ken-Ichi Akao(
Part:
Contributor)
Maruzen
2018.05
ISBN:
9784621302927
Declining Discount Rate (Society for Environmental Economics and Policy Studies ed. Handbook of Environmental Economics and Policy Studies)
Ken-Ichi Akao(
Part:
Contributor)
Maruzen
2018.05
ISBN:
9784621302927
Precautionary Principle (Society for Environmental Economics and Policy Studies ed. Handbook of Environmental Economics and Policy Studies)
Referee experience: Environmental Economics and Policy Studies, ETRI Journal, International Journal of Global Environmental Issues, Metroeconomica, Resource and Energy Economics, Journal of Economic Dynamics and Control, International Journal of Economic Theory, Journal of Public Economic Theory, Ecological Research, Journal of Forest Research, Journal of Difference Equations and Applications, Mathematical Social Sciences, Applied Economics, Environmental and Resource Economics, American Journal of Agricultural Economics, Social Science Quarterly, Journal of Mathematical Economics, Japanese Economic Review, Environment and Development Economics, Journal of Economic Theory
Research Projects
Research Projects
Study on the Schelling's Paradox of Global Warming and Altruism
Discount rate and international environmental agreement in climate change
Project Year :
2018.04
-
2021.03
Application of nonlinear equilibrium dynamics to global environmental issues
Project Year :
2011.11
-
2016.03
View Summary
Global environmental issues such as the global warming and the biodiversity loss have serious long-term consequences and several other novel features. Using nonlinear economic dynamics models incorporating those features, we analyzed the interaction between the society and the issues. The models are: dynamic game model with an environmental asset, non-concave optimal growth model, endogenous growth model with large and unpredictable shocks, and a social planner model for agents with non-exponential discounting. From them we have several new results as shown in “Research Performance” below. Some of them are found in our papers published in international journals. We also surveyed some related research issues that are recently extensively studied. They include the axiomatic approaches to intergenerational equity and the declining discount rate for social cost/benefit analysis. Our results help to understand why and when we choose an unsustainable path and to consider how to avoid it
Identifying Critical Natural Capital for Environmental Risk Management
Project Year :
2006.04
-
2012.03
View Summary
The natural capitals have their distinct structure, function and dynamism, providing us with livelihood and defining our lives as a basis of our various daily activities. It appears that the recent circumstances surrounding the natural capitals are changing increasingly, such as rapid development towards globalization, and the number of challenges needing solutions seems to be ever on the increase. This research attempts to elucidate the following : how we may define the criticality of natural capital, how to develop them into workable concepts, to use them as beacons in taking relevant and necessary policy measures and community activities, and to ameliorate such measures and activities further
1)We considers the simplest DRM, which permits either free or no copying, with incomplete information about the type of consumer. We first obtain results concerning separability of consumers in a general situation, and show that there is a critical type of consumer. A higher utility type selects a menu of free copying whereas a lower one chooses not to copy. In a two-type model we indicate that optimal pricing for a producer is different from that under two-part tariffs. This price strategy brings about greater profits and social welfare if, and only if, self production is more efficient than that of a producer. 2)Although producers seek to protect their content from copyright infringement on the Internet, it is not easy, being similar to preventing illegal parking. For such a situation, they must not only consider copyright protection, but also the effect on transaction costs from such unauthorized file-sharing. We consider whether copy control is effective in order to reduce damages to the producer's profits and to increase social welfare. Since copy control makes copying physically impossible, it decreases consumer benefits, compared with those from no copy control. We show that transaction costs of unauthorized file-sharing determine the effectiveness of copy control and obtain the conditions under which there is an incentive for a producer to introduce copy control while being compatible with an incentive from a social perspective.
本研究は、持続可能な発展と共有地の悲劇のそれぞれを考察することを課題とした。1)持続可能な発展に関して、消費が環境負荷を与える(ゴミ問題のある)経済での最適経路を、Aghion and Howitt(1998,5章)を基礎とする内生的成長モデルによって検討した。環境の保全あるいは改善をともなう持続経路の実現には、生産が環境負荷を与えるモデルと同様に、消費の異時点間代替弾力性(以下、IES)の逆数が1以上でなければならない。加えて、(1)人的資本の限界生産性その他のパラメータとの関係において、自然の自浄能力は十分に高いか、あるいはIESの逆数がある上限を超えてはならない、(2)リサイクル技術改善および自然の自浄能力を維持するために必要な労働投入量がある水準以下にとどまる必要がある、ということが明らかとなった。以上の結果は、直観的には明らかかもしれないが、理論分析としては新しい結果である。またリサイクル技術へのR&D、自然の自浄能力と経済成長率との関係は、持続可能な発展を実現する上で重要な含意を有すると考える。2)共有地の悲劇に関しては、一状態変数の微分ゲームを用いて、各プレーヤーの部分ゲーム完全均衡戦略が、一意かつ効率的トラジェクトリをもつことになる政策を考察した。この政策は、あたかも"自然状態"から貨幣経済への移行をもたらすようなものである。政策が機能するには、政策の信頼性が必要である。現実の環境問題において信頼性が保証されるケースを論じた。また、政策はそれを行う政府にとってはopen-loop strategyであり、政府は部分ゲーム完全性を満たさないことを指摘した。なお、分析に用いられたモデルは資源の外部性を含まない。外部性を含むケースでは、政策はプレーヤー間の戦略的依存関係を消し去ることができず、また非凸性の問題が現れる。このケースの考察は、今後に残された課題となった
A Political Economy Model of Natural Resource Exploitation
Forestries in Japan & Korea Affected by Environmental Issues
Project Year :
1996.04
-
1999.03
View Summary
1996 : The field research to Korean and the Northwest of USA(1) With the timber export restrictions of the timber-production countries, Japan has increased imports of timber processing products and Korea has diversified the log import origins. As for the imports of timber processing products of both countries, the wooden board and panel are increasing instead of lumber and plywood.(2) The demands to forest recreation both in Japan and in Korea have been increasing for this decade.(3) In the northwest of USA, the protection movement to salmon has just begun. On the other hand, the business of timber processing industries, which were made severe with the timber felling limitation policy, have been improved by the relaxation on the felling limitation.1997 : The field research to the western part of Canada, the southern part of Korea, East-Kalimantan of Indonesia(1) Log production level of Canada was stable but the quality has been deteriorating. The earning rates of forest related companies have reduced by the enforcement of Forest Management Act in British Colombia.(2) In Japanese forestry regions, forestry management has been declining gradually. Forest owners intend to make special quality logs such as a polished fancy log and to extend cutting age.(3) In Korea, incorporation forestry business of officials and privates is developed to make the effective use and the improvement of the function on forest resources. The citizen is using wood products such as the sycamore sap and the chestnut in various ways. The repulsion of Korean mass communication to the felling and forestry road is strong.(4) Indonesia may start log export because the power of APKINDO has been declining under the counsel of IMF.Also, peoples in East-Kalimantan area were severely damaged as a result of the forest fire.1998 : The field research to the southern part of USA and New Zealand(1) Most of Southern yellow pine that was planted in the southern part of USA is coming cutting age and the production volume is increasing. Main targets of the supply are domestic market and the Caribbean Sea region. So, the supply to Japan and Korea will not increase conspicuously.(2) The log production and export in NZ are increasing rapidly with a background of plentiful Radiata pine forest. NZ is promoting export to China and South-east Asian countries instead of Australia who will be able to provide timber for herself.With the log export regulation policies and ban policies in the timber production countries, most of the forest related industries of Japan and Korea have been declining rapidly but the demand for forest recreaton is increasing
A diversity function derived from the Nehring-Puppe's attribute approach possesses the nesting property only if there are at most two attributes that determine the value of diversity. The validity of the precautionary principle depends on the preference. The situation that the principle is unanimously supported has not yet been known. An optimal forest use model and a trade model on forest products have been analyzed
SAET 2019, Ischia (Napoli. June 30- July 6)
(Napoli, Italy)
Society for the Advancement of Economic Theory
Presentation date:
2019.07
Akao,K., K. Uchida and Y. Wasa. International Environmental Agreements as an Equilibrium Choice in a Differential Game (National Institute of Ecology, Choongnam, Korea. 8/27-28)
Ken-Ichi Akao
KEEA 2018 Summer Conference
(National Institute of Ecology, Choongnam)
Korean Association of Environmental Economics
Annual conference of Society of Environmental Economics and Policy Studies, 2017
(Kouchi University of Technology)
Presentation date:
2017.09
Akao,K., K. Uchida and Y. Wasa. International environmental negotiations and agreements: A differential game interpretation.
Ken-Ichi Akao
7th Congress of EAAERE at Singapore (8/5/2017 - 8/7/2017)
East Asian Association of Environmental and Resource Economics
Presentation date:
2017.08
Akao, K. and H. Sakamoto. A theory of disasters and long-run growth
Ken-Ichi Akao
IASS and RIEEM Workshop: Economic Analysis on Disasters and Adaptations
Presentation date:
2016.12
Symmetric Stationary MPNE in Differential Games
Ken-Ichi Akao
RIEEM Workshop “Intergenerational equity, discounting and international agreement in global warming”
(Waseda University)
Presentation date:
2016.11
When society moves away from sustainable development
Ken-Ichi Akao
Society for Environmental Economics and Policy Studies 2016 Meeting, Aoyama Gakuin University, Tokyo
Presentation date:
2016.09
When society moves away from sustainable development
Ken-Ichi Akao
[Invited]
Seminar at School of Environment, Northeast Normal University, Changchun, China
Presentation date:
2016.08
An Economic Analysis of the “Home Appliance Eco-Point System” in Japan
Ken-Ichi Akao
Korean Environmental Economic Association, Pusan, Korea
Presentation date:
2016.08
When society moves away from sustainable development
Ken-Ichi Akao
[Invited]
Korean Environmental Economic Association 2016 Summer Meeting, Pusan, Korea
Presentation date:
2016.08
Akao, K., T, Kamihigashi and K. Nishimura, Critical capital stock in a continuous time growth model with convex-concave production function
Ken-Ichi Akao
6th Congress of the East Asian Association of Environmental and Resource Economics. Kyushu Sangyo University, Fukuoka
Presentation date:
2016.08
Declining Discount Rate and Environmental Economics
Ken-Ichi Akao
The 20th Anniversary Meeting of the Society of Environmental Economics and Policy Studies (Kyoto University, Sep 18 - 20, 2015)
The Society of Environmental Economics and Policy Studies
The 5th Congress of EAAERE (Academia Sinica, 2015/08/05-07, Taipei, Taiwan)
(Taipei)
Presentation date:
2015.08
Ken-Ichi Akao and Hiroaki Sakamoto: A Theory of Disasters and Long-run Growth
Ken-Ichi Akao
15th SAET Conference on Current Trends in Economics (University of Cambridge, July 27-31, 2015)
Presentation date:
2015.07
Ken-Ichi Akao, Takashi Kamihigashi, Kazuo Nishimura: Critical capital stock in a continuous time growth model with convex-concave production function
The 9th International Conference on Nonlinear Economic Dynamics: NED 2015. June 25 - 27, Chuo University, Tokyo
Presentation date:
2015.06
Ken-Ichi Akao, Takashi Kamihigashi, Kazuo Nishimura: Critical capital stock and optimal steady states in a continuous time aggregate growth model with convex-concave production function
Workshop on Environmental Economics, March 13 - 14, 2015. National Institute for Environmental Studies, Tsukuba
Presentation date:
2015.03
Optimality of sustainable development: The preference constraint and the assimilation capacity of the environment
Workshop on the inclusive wealth accounting and ecosystem services (Graduate School of Environmental Studies, Nagoya University )
Presentation date:
2014.11
Ken-Ichi Akao, Hiroaki Sakamoto: A theory of disasters and long-run growth
5th World Congress of Environmental and Resource Economists, June 28 - July 3, 2014, Istanbul Lutfi Kirdar Convention & Exhibition Centre, Turkey
Presentation date:
2014.06
Ken-Ichi Akao, Hiroaki Sakamoto: A theory of disasters and long-run growth
4th Congress of East Asia Association of Environmental and Resource Economics, February 12-13, 2014, BEXCO at Busan, South Korea
Presentation date:
2014.02
Ken-Ichi Akao, Takashi Kamihigashi, Kazuo Nishimura: Critical capital stock and optimal steady states in a continuous time aggregate growth model with convex-concave production function
1st Asia-Pacific Conference on Economic Dynamics, November 21 - 22, 2013, University of Economics and Law, Ho Chi Minh City, Vietnam
Presentation date:
2013.11
Ken-Ichi Akao, Gerhard Sorger: On the sustainability of a common property resource: An implication from dynamic game theory
Presentation date:
2013.09
Ken-Ichi Akao, Tapan Mitra, and Gerhard Sorger: Some rationalizability results for dynamic games
PET13-Annual Conference of the Association for Public Economic Theory (Catolica Lisbon, Lisbon, Portugal. July 4--7, 2013)
Presentation date:
2013.07
Ken-Ichi Akao, Gerhard Sorger: On the sustainability of a common property resource: An implication from dynamic game theory
The 3rd Congess of the Association of East Asian Environmental and Recource Economics, February 20-22, HuangShan, China
Presentation date:
2013.02
気候変動問題の経済学的特徴とその理論的問題
環境経済・政策学会2012年大会(東北大学 9/15, 16, 2012)
Presentation date:
2012.09
Ken-Ichi Akao, Takashi Kamihigashi, Kazuo Nishimura: On the critical capital stock in a continuous time aggregate growth model with a convex-concave production function
12th SAET Conference, June 30 - July 3, 2012, University of Queensland, Australia
Presentation date:
2012.07
Ken-Ichi Akao, Gerhard Sorger: On the sustainability of a common property resource: an implication from dynamic game theory
Presentation date:
2012.06
Ken-Ichi Akao, Shunsuke Managi: A tradable permit system in an intertemporal economy- a general equilibrium approach-
Presentation date:
2011.09
Optimality of sustainable development and the preference constraint
PACE2011 International Symposium on China’s Environment, Economy and Policy (Tachee Island Holiday Hotel, China, 7/12-7/16)
Presentation date:
2011.07
On the preference constraint for sustainable development to be optimal
18th Annual Conference of the European Association of Environmental and Resource Economists (University of Rome, Rome, 6/28-7/4)
Presentation date:
2011.07
On the preference constraint for sustainable development to be optimal
Presentation date:
2011.05
Optimal forest program when the carbon sequestration service of a forest has value
Seminar of Department of Economics at Hawaii University, Manoa (3/7)
Presentation date:
2011.03
On the preference constraint for sustainable development to be optimal
1st Congress of the East Asian Association of Environmental and Resource Economics (Hokkaido University, Sapporo, 8/18-19)
Presentation date:
2010.08
Ken-Ichi Akao, Shunsuke Managi: A tradable permit system in an intertemporal economy- a general equilibrium approach-
Forth World Congress of Environmental and Resource Economists (Montreal, Canada , 6/28-7/2)
Presentation date:
2010.06
On the preference constraint for sustainable development to be optimal
PET10-Annual Conference of the Association for Public Economic Theory (Bogazici University, Istanbul, Turkey, 7/25-27)
Presentation date:
2010.06
On the preference constraint for sustainable development to be optimal
長期プロジェクトの費用便益分析で用いるべき割引率に対するモデルについて考察した。その中心的な課題は確率的割引率の定式化であることがわかった。不確実性を含む通時的交換経済モデルであるいわゆる Lucas Tree に基づいた C. Gollier の一連の研究がある。より抽象度の高いモデルは L. Hansen and J. Scheinkmanによって分析されている。最も新しい研究は Qin and Linetsky (Econometrica, 2017) である。確率過程と確率制御に関する深い知識が必要となる。
地球環境問題への非線形均衡動学の応用として、次の3つの研究を行った。(1)非凸生産関数最適成長モデルにおけるクリティカル・キャピタル・ストック(CCS)の特徴づけ。(2)ダイナミックゲームと最適成長モデルに関するラショナライゼーション。(3)市民の自己監視を利用した環境政策。(1)は京大経済研究所西村和雄教授、神戸大経済経営研究所上東貴志教授との共同研究成果として、CCSが割引率の連続かつ狭義単調増加関数であること、CCSが存在する上限の割引率において、それは内点定常解と一致するヘテロ・クリニック・ポイントとなること、限界効用の弾力性が一定の効用関数のケースで、この上限の割引率は、同弾力性を十分に大きくすることで生産関数の変曲点の傾きに好きなだけ近づけることができこと、一方、同弾力性を十分に小さくすることで平均生産性の最大値(<変曲点の傾き)に好きなだけ近づけることができることを明らかにした。(2)はConnell大Tapan Mitra教授、Vienna大Gerhard Sorger教授との共同研究成果として、生産技術を不変として、いかなる最適成長モデルの最適経路もダイナミックゲームの均衡経路と解釈できること、逆にあるダイナミックゲームの均衡経路のあるクラスは最適成長モデルの最適経路と一致させることができることを示した。特に興味深い結果としてLevhari-MirmanのGreat Fish Warモデルでは、その生産関数を共通とし効用関数のクラスを消費のみに反応するものとするとき、ダイナミックゲームの線形戦略は、まったく同じ瞬間的効用関数とより大きな割引率をもつ最適成長モデルの最適方策関数と一致する。つまり、戦略的依存関係は割引率によって調整される。(3)はHoseo大のGeum Soo Kim教授との共同研究成果として、ゴミの不法投棄のような政府のみでは十分な環境政策を実行できないか、実行するには多大なコストが発生する状況で、人々の自己監視によって効果的な環境規制が可能となるか、またそうした自己監視が機能するための社会共通資本の果たす役割を進化ゲームの枠組みで分析した。社会を構成する3つのタイプの主体、すなわちルールを守る者、ルールを破る者、そしてルールを守るだけでなくルールを破る者を告発する者の人口変化が分析の対象である。ルールを破る者が絶滅するための条件を政府の政策および社会共通資本のダイナミクスとの関係において明らかにした。
生物多様性に関して、Nehring and Puppe (2002) の多様性関数に対する属性アプローチについて詳細に検討した。生態学の多様度の概念とどのように結び付けるべきかを考察したが、未だ結果は出ていない。 ナイト流の不確実性に関して、基礎となるGilboa and Schmeidler (1989) の理論およびその連続時間モデルへの拡張であるChen and Epstein(2002)、その環境問題への応用であるAsano (2005)等の論文を研究した。幾何ブラウン運動を元にして、特定のdesnsity generatorと制約条件(kappa-ignorance)のもとで「予想」の集合をつくると、ナイト流不確実性下での最適制御は、ドリフト項のみを修正した幾何ブラウン運動の確率最適制御問題に帰着する。この手法は非常にトラクタブルである。しかし、極めて制約的でもある。より一般的な結果を得るにはどうすればよいかを考察したが、未だ結論は出ていない。なお、Giboa-Schmeidlerの有限集合モデルでの公理系をChen-Epsteinが連続時間の動学的世界に拡張する際に微妙な問題があるように感じた。 以上、本研究では、生物多様性の経済分析として、これら二つのトピックスを研究したが、形式的に両者は確率キャパシティを通じて関係しあっている。今後、有限確率の枠組みの中でそのつながりを明らかにしたい。また連続時間への拡張であるChen-Epsteinは非常に難解な論文である。超準解析によって見通しのよい拡張と応用ができないか、今後研究していきたい。
地球環境問題を考える上で重要な要素として世代間衡平と人口問題がある。本研究は、世代間衡平の観点から望ましい資源配分や人口経路とはいかなるものかを考察した。本研究では、各世代が隣り合うかあるいは重なり合う世代が資本(世代を超えて存在するもの)の扱いに関して対等な権利を有するという仮想的な状況を想定し、そこで行われる交渉の結果(ナッシュ交渉解)の列でサブゲーム完全なものを世代間衡平経路と定義する。特定のモデルに関してではあるが、そのような交渉解の列が、割引のあるラムゼーモデルの解によってミミックできること、人口が交渉の対象となるときの解は、Barro and Becker (1989)の産子数選択の動学モデルの最適解を思わせるものになること、そして世代重複モデルでは世代間衡平経路は生成的に非効率であることなどを明らかにした。 本研究の世代間衡平の定義は手続き上の衡平性に基づくものといえる。これに対して、従来、経済学では評価上の衡平性(割引なしのラムゼーモデル)か、結果上の衡平性(平等主義モデル、ロールズ流のミニマックス経路)が考察されてきた。平等主義は、経済が成長可能であるとき(つまりラムゼーモデルの最適経路が右上がりであるとき)、われわれの世代間衡平観に反する経路を示唆する。一方で、ラムゼーモデルは、経済動学の始祖であるRamsey(1928)自身、割引が倫理的に正当化できないと主張すると同時に、ゼロ割引率が容認できないような高い最適貯蓄率を示唆することを指摘している。本研究は、このような状況に対して、手続き上の衡平性を考えることで現実に容認可能な世代間衡平経路を提案している。平等主義経路もラムゼー経路もサブゲーム完全ではあるが、将来世代は現在世代の決定に対して何ら異議申し立てができない。このような経路は、手続き上の衡平性を欠いている。