Does Airport Preferential Policy Aggravate the Competition of Aviation Hubs in Central and Western China? Based on the Investigation of 78 Airports

Table 1

The main indicators and calculation methods.

Variable type	Variable name	Variable symbol	Variable definition
Dependent variables	Airport cargo traffic	lncm	The logarithm of airport cargo throughput
	Airport passenger flow	lntra	The logarithm of airport passenger throughput
	Economic level	lngdp	The logarithm of actual regional gross domestic product
	Industrial structure	sec	Added value of manufacturing industry/regional GDP
Control variables	Population	lnpop	The logarithm of the population at the end of the year
	Facilities qualification of airports	lnrf	The logarithm of the number of airport takeoffs and landings
	Population density	pd	Population/administrative area
	Tourism attraction ability	lnta	The logarithm of the number of people employed in the accommodation and catering business
	Per capita urban road area	proad	Urban road area/population
	Human capital	lntea	The logarithm of the number of full-time teachers in colleges
	Employment situation of secondary industry	esis	The number of employed people in the manufacturing industry/population
	Government intervention	gov	Government budget expenditure/government budget revenue