Hierarchical Characteristics and Proximity Mechanism of Intercity Innovation Networks: A Case of 290 Cities in China

Table 1

Definitions of variables in the proximity mechanism model for intercity innovation networks.

Variable	Index	Definition	Measure method
Explained variable	Innovation cooperation	Ties for innovation cooperation between two cities	Number of joint invention patents for cities i and j
	Geographical proximity	Geographical proximity between two cities
Explanatory variable	Institutional proximity	Degree of similarity in institutional environments between two cities	1 or 0
	Cognitive proximity	Similarity in technical knowledge structure between two cities
	Innovation performance	City’s technological innovation capability	Number of invention patents
Control variable	Innovation input (RDE)	R&D expenditure
	Innovation talent input (HUC)	Human capital	Number of personnel with bachelor degree or above
	Economic development (GPC)		GDP per capital