The total number of trade relations of a country in complex network model is calculated by degree.
Out-degree is the number of export relations a country has with others, and in-degree is the number of
import relations. The values of out-degree and in-degree can reflect a country’s importance in the network
considering only relationships. The total trade volume of a country in complex network model is
calculated by weighted degree. Weighted degree reflects a country’s importance in the network
considering both relations and volume