## 4 Results and Discussion  
### Reconstitution of IO Tables for Comparative Analysis  
This study intends to utilize the most recently published IO tables in South Korea and Japan. In this respect, the IO tables in South Korea and Japan are for 2019 and 2015, respectively. The authors think that it can be possible and meaningful to compare the analysis results using IO tables for different years for the two countries in two points. First, because most of the results presented in this study mean the effect of a monetary unit caused by a change in monetary value by one unit, the results for one country can be compared with those for another country. In other words, as the results represent relative values, not absolute values, they can be compared with each other between countries. Although the employment-inducing effect and the price-pervasive effect are interpreted somewhat differently, they can be compared between countries because the currency unit is unified using the exchange rate, or the results mean the effect per unit. Second, the target years of the IO table are different in South Korea and Japan, but this does not make comparability difficult. What is finally dealt with in this study is not the input coefficient matrix, but the input inverse matrix. The former may not be stable over time, but the latter is known to be quite stable over time [41; 55; 56]. In addition, similar reasoning is possible for the output coefficient matrix and the output inverse matrix. Even if the target years of the IO table differ from each other as 2015 and 2019, a difference of about 4 years will not have a significant effect on the stability of the results. Therefore, the main analysis results for the two countries can be compared.  
The category classification method of IO table in South Korea consists of four elements: basic-scale 381-sector, small-scale 165-sector, medium-scale 83-sector, and large-scale 33-sector. The category classification method of the IO table in Japan consists of three elements: small-scale 187-sector, medium-scale 107-sector, and large-scale 37-sector. In other words, sector classification methods are different for the two countries. However, for a comparative analysis, it is necessary to match the sector classification of the IO tables for the two countries. Therefore, this study reconstituted both the small-scale 187-sector in Japan and the small-scale 165-sector in South Korea based on the large-scale 33-sector in South Korea [57; 58].  
In the process of that reconstitution, attention was paid to two things. First, the NG supply sector, which is the subject of research in this study, was dealt with independently. It does not include any offshore activities and transportation and focuses on domestic infrastructure. Therefore, as the 33-sector classification method is adopted, the NG supply sector is added. Second, two sectors (\"Transport equipment\", \"manufacturing services and repair services of industrial equipment\") in the 33-sector classification method were integrated into a new sector called \"Transport equipment, manufacturing services, and repair services of industrial equipment\". In the 33-sector classification method, as one sector increased and one sector decreased at the same time, the total number of sectors was eventually maintained at 33. The finally adopted category classification results are contained in Table 1. The respective, complete reconstitution maps of the two countries are shown in Appendix A.