Table 3.

Definitions of variables and data sources.

Variable	Definition	Source
GDP	Economic growth: cities’ real GDP	CUSY
ED	Ecological environment damage: cities’ eco-environment damage index	Calculation
K	Physical capital: estimated using ‘perpetual inventory method’	Calculation
L	Human capital: employed persons in urban units	CUSY
E	Energy input: annual total urban electricity consumption	USY
EC	Ecological environment construction: cities’ eco-environment construction index	Calculation
MIL	Modified Input-oriented Luenberger productivity indicator: ecological total factor productivity of cities in the Yellow River Basin	Calculation
FD	Fiscal decentralisation: urban annual per capita fiscal expenditure / (urban annual per capita fiscal expenditure  +  national annual per capita fiscal expenditure)	Wind Database
ER	Environmental regulation: urban pollution treatment cost / cities’ added value of secondary industry	Wind Database
IND	Industrial structure: cities’ tertiary sector value added/ cities’ GDP	CUSY
FIN	Financial development: balance of deposits and loans of financial institutions / cities’ GDP	USY
URB	Urbanisation level: size of cities’ urban population / total population	CUSY
OPEN	Opening level of cities: total foreign direct investment / cities’ GDP	USY
RD	Research and development investment: cities’ R&D investment / cities’ GDP	CUSY
POP	Population density: total cities’ annual average / total urban area	USY

Notes: Calculation: Calculated by vertical and horizontal scatter grade method, CUSY: China Urban Statistical Yearbook, USY: Urban Statistical Yearbooks of cities in the Yellow River basin. For the data used in this study, the timeframe was from 2003 to 2019.