The Study of the Spatial Heterogeneity and Structural Evolution of the Producer Services Trade Network

Table 1

Network analysis indicators.

Indicators	Formulation	Index explanation	Actual meaning
Network density		refers to the proportion of the actual number of node connections in the network to the maximum number of possible node connections.	The activity of producer services trade links among countries.
Average degree		refers to the average of the degrees of all nodes, represents the degree of node. .	The connectivity of the whole trade network.
Average path length		refers to the average number of the shortest path between each pair of nodes, represents the shortest path between nodes and .	The transmission efficiency of trade network.
Average clustering coefficient		is the mean value of the clustering coefficients of all nodes. represents the clustering coefficient of node .	The degree of aggregation and adjacency of trade network.
Degree centrality		describes the ability of direct contact of node with others.	The possibility of direct trade links between a country and other countries.
Closeness centrality		refers to the sum of the shortest path between an individual node and all other nodes.	The relative spatial accessibility of countries in trade network.
Betweenness centrality		refers to the probability that a node is in the shortcut between node pairs. is the number of shortcuts between node and . is the number of shortcuts between node and that passes through the node .	The transfer function of countries in trade network.
Node strength		is the sum of weights of all edges connected to the node . In the directed network, it can be divided into out-strength and in-strength.	Trade volume between countries in a weighted trade network.
Core degree		By iterating different pattern matrices to obtain the maximum value . At this time, is the actual corresponding core-periphery structure matrix. represents the core degree of node, is the element in adjacency matrix, is the element in pattern matrix of the core-periphery structure, and represents the correlation between matrix and matrix .	The status and importance of a country in trade network.