This study focuses on the types of petroleum-derived product materials, which are intermediate goods, to measure the impact of the plastic bag charge policy implemented in Japan in July 2020 on the amount of plastic bags produced. Using difference-in-differences, synthetic control, and synthetic difference-in-differences methods on material data from 2007 to 2023, the plastic bag charge policy appears to have resulted in a 1.097 kg reduction per person in the sales of high-density polyethylene. This is equivalent to a reduction of 13.88 billion plastic bags in Japan as a whole, empirically confirming the effectiveness of this plastic bag charge policy.

Concerning capacity building for policy proposals and the ability to solve environmental problems, this paper clarifies the potential of youth climate assemblies conducted by collaboration between universities and local governments. The paper also shows the significance of the youth climate assembly as a participative approach for environmental policy. A youth climate assembly conducted in the class of Faculty of the Law, Shinshu University submitted a policy proposal for the Zero-carbon Matsumoto plan to the mayor of Matsumoto City. Most of the students who participated in the assembly came to think of climate change as an issue that affects them, and learned how to create a policy proposal. Their proposal was reflected in the Zero-carbon Matsumoto plan to some extent, demonstrating that the youth climate assembly played a role as a participative approach for climate change policymaking.

Best-worst scaling (BWS) is increasingly used in environmental economics and policy studies to analyze citizen and consumer preferences. We describe its characteristics and explain how to create BWS questions and how to analyze the response data obtained. We then develop a “Best-worst scaling with Excel” approach that enables the creation of BWS questions and the analysis of responses to be conducted with Excel and explain how to use it.

This paper discusses the integration of natural science knowledge into social science research, particularly focusing on climate change. It highlights how social scientists can use natural science insights, specifically through climate models, to study and address climate-related issues. As an application, the paper explains how one can estimate the social cost of greenhouse gases by combining the output of climate models, climate emulators, and economic models.