The structure and nodes' role of the world coal trade network

This paper employs the network approach to study the structure and nodes' role of the world coal trade network. Based on the bilateral coal trade data of 212 countries (or regions) over the period from 2001 to 2010, this study analyses the world coal trade network, the network's directionality and heterogeneity, and the roles of network nodes. It is found that the size of the world coal trade network is relatively stable, while the trade links and volume have been growing overtime. Because of the buyer-seller dual structure between exporters and importers, the network shows strong directionality. It also exhibits heterogeneity because of the uneven distribution of trade among different countries. In general, most countries can be classified as the in-nodes, followed by the middleman-nodes, then the cycle-nodes and out-nodes. Finally, the web shows a remarkably significant core-periphery structure and core-half-anedge-edge structure and the core layers of each model are quite stable.