実験社会科学 - 実験が切り開く21世紀の社会科学 -

樽井　礼 （ハワイ大学経済学部准教授）
"Cooperation on climate change mitigation: theory, simulations, and experiments"

Abstract: The first part of the talk summarizes a research (joint with Charles Mason and Stephen Polasky) that models greenhouse gas (GHG) emissions as a dynamic game. Countries’ emissions increase atmospheric concentrations of GHG, which negatively affects all countries' welfare. We analyze self-enforcing climate-change treaties that are supportable as subgame perfect equilibria. A simulation model illustrates conditions where a subgame perfect equilibrium supports the first-best outcome. In one of our simulations, we explore the structure of a self-enforcing agreement that achieves optimal climate change policy, supportability of the agreement under a range of plausible parameter values, and which countries have the most to gain from such an agreement. In particular, the findings delineate how the supportability depends on the countries’ discount factors as well as the slopes of the marginal cost of GHG emission reduction and the marginal damages due to climate change. The second part of the talk summarizes the preliminary results of experiments (joint with Katerina Sherstyuk, Tatsuyoshi Saijo, and Majah-Leah V. Ravago) that explore strategic behavior in the presence of dynamic externalities. Using experiments of a dynamic game with a random time horizon, we contrast the findings from a game with long-lived players and those from a game played by generations of different players.