## 英文概要

In light of the overall resource dependence of the Japanese economy in international supply chains, this study was conducted to develop a new quantitative indicator of the contribution of reducing, reusing, and recycling (3R) activities involving Japan’s goods and services to both quantitative and qualitative reduction of resource dependence and to measure the indicators for major rare metals necessary for low-carbon technologies. The study consisted of the following three themes. Theme 1 was “to understand the condition of international material flow of rare metals and explain its structural relationship with Japan,” Theme 2 was “to design the framework for risk assessment of resource dependence and develop a quantification method,” and Theme 3 was “to measure the risk indicator of resource dependence for the 3R activities on goods and services in Japan.”

The results were the following. In Theme 1, the form of international trade through which rare metals moved from countries of origin to consumption countries was examined using material flow analysis (MFA) to elucidate the interdependence relations of respective countries with respect to rare metals trade. To do this, the study developed a methodology that would enable MFA of rare metals based on a global system boundary encompassing 231 countries and regions. This analysis specifically examined rare metals of 10 types necessary for low-carbon technologies, including neodymium (Nd), cobalt (Co), platinum (Pt), nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), and lithium (Li). Subsequently, a global link input-output model (GLIO) was applied to identify the parts of international flow of rare metals on which Japanese economy caused directly and indirectly. This means that Japanese economy depends on this identified parts of the international flows of rare metals.

In Theme 2, structural characteristics of the international flow of rare metals were analyzed to consider the qualitative factors of resource dependence, in addition to the amount of consumption as a quantitative factor required for the supply risk indicators of rare metals. By positioning the political risk of resource mining countries existing in international flows and trade risk latent in international supply chains from processing after mining to end products as qualitative factors, the study developed a method of MFA involving those risk factors. Furthermore, as another qualitative factor, the study classifies the international supply chains of rare metals into three groups by focusing on differences in social and technological level of each country, and identified flows that preferentially need technological improvement on rare metal use. In addition, the study developed a new technique to extract the international transactions that constitute the core of the international flow of rare metals and a visualization method that is expected to yield high visibility to help all stakeholders understand the complex international flow easily.

Finally under Theme 3, the indicators of reduction in Japan’s international dependence on rare metals through reducing, reusing, and recycling Japan’s goods and services was designed using the methodologies developed under Themes 1 and 2. Such indicators of reduced international dependence through reducing, reusing, and recycling can be derived from the intensity of goods and services representing how much Japan’s international dependence is reduced by avoiding unit of production (one million yen) of goods and services. The study calculated the intensity of approximately 800 goods and services among the domestic products and imports of Japan. A methodology to convert the extended years of lifespan to the amount of reduced demand was also developed to derive the indicator of “reusing.” Finally, a model to estimate future demand for household consumption was developed by incorporating the population reduced by the declining birth-rate and aging society and changes in household structure. Based on the estimate future demand, changes in