First of all, from the enterprise-level data (micro-data) of Japanese industrial statistics, we can see how high the actual benefits of Japanese parts manufacturers are. Parts manufacturers have always been one of the sources of Japanese automobile industry. Okamoto (1999) came to the conclusion that the economic benefits of Japanese parts enterprises (including joint ventures) entering the American market lag behind those of American suppliers in the North American market. There are two reasons for this. One is that the source of the competitiveness of Japan's automobile industry is to assume that there are excellent parts companies, which is inherently problematic. Another is that in the United States, where the labor market and industrial structure are completely different, the absolute advantages held by Japanese parts companies may not be fully exerted. We can find out the reason by comparing the economic benefits of Japanese parts enterprises in the United States and Japan entering the North American market.