Hierarchicality of Trade Flow Networks Reveals Complexity of Products
Peiteng Shi1, Jiang Zhang1*, Bo Yang2, Jingfei Luo1
1 School of Systems Science, Beijing Normal University, Beijing, China, 2 Ministry of Commerce of the People’s Republic of China, Beijing, China

Abstract
With globalization, countries are more connected than before by trading flows, which amounts to at least 36 trillion dollars today. Interestingly, around 30{60 percents of exports consist of intermediate products in global. Therefore, the trade flow network of particular product with high added values can be regarded as value chains. The problem is weather we can discriminate between these products from their unique flow network structure? This paper applies the flow analysis method developed in ecology to 638 trading flow networks of different products. We claim that the allometric scaling exponent g can be used to characterize the degree of hierarchicality of a flow network, i.e., whether the trading products flow on long hierarchical chains. Then, it is pointed out that the flow networks of products with higher added values and complexity like machinary, transport equipment etc. have larger exponents, meaning that their trade flow networks are more hierarchical. As a result, without the extra data like global input-output table, we can identify the product categories with higher complexity, and the relative importance of a country in the global value chain by the trading network solely.
Citation: Shi P, Zhang J, Yang B, Luo J (2014) Hierarchicality of Trade Flow Networks Reveals Complexity of Products. PLoS ONE 9(6): e98247. doi:10.1371/journal. pone.0098247 Editor: Dante R. Chialvo, National Scientific and Technical Research Council (CONICET)., Argentina Received January 18, 2014; Accepted April 16, 2014; Published June 6, 2014 Copyright: ß 2014 Shi et al. This is an open-access