Centralized flow structure of international trade networks for different products

All countries in the world are connected each other and one country´s export may impact other countries deeply through global value chains as the development of globalization. Owing to the regional differences in culture and resources, some countries may dominate the producing and exporting of one product in the global trade. This paper treats international trade webs of different products as flow networks to reveal a power law relationship between the goods flow through a country i (A_i) and the power impact of i to other countries (C_i) in the trade network of a specific product, C_i~A_i^η. Where the exponent η can be used to reflect the degree of the impact concentration on high through flow nodes of the whole network, it is centralized or decentralized. We discover that most of trade networks are centralized (i.e., η >1) and the manufacture products with high added values such as machinery equipment, iron and chemical products have larger exponent, i.e., their trade networks are more centralized than the ones of the primary products like agricultural and raw materials. This also means that the flow structure of the former is more centralized than the latter.