Table 1 The index system for coupling coordination analysis between socio-economy and environment.

From: Exploring socioeconomic and environmental coordination in the Yangtze River Delta Region using a game theory stepwise-cluster factorial coupling coordination model

System

Code

Indicator

Unit

Effect

Socioeconomic system

X1

Gross domestic product (GDP) per capita

10,000 Yuan/person

Positive

X2

Income per unit land area

10,000 Yuan/km2

Positive

X3

Engel’s coefficient

–

Negative

X4

Proportion of the added value of tertiary industry to GDP

%

Positive

X5

Import and export value per capita

$/person

Positive

X6

Population density

person/km2

Positive

X7

Urbanization rate of permanent residence

%

Positive

X8

Number of hospital beds per 10 thousand people

–

Positive

X9

Number of college students among 10 thousand people

person

Positive

Environmental system

Y1

Industrial wastewater discharge per unit of GDP

ton/Yuan

Negative

Y2

Fine particulate matter (PM2.5) concentration

µg/m2

Negative

Y3

Energy consumption per unit of GDP

tce/Yuan

Negative

Y4

Utilization rate of non-hazardous industrial solid waste

%

Positive

Y5

Centralized treatment rate of domestic sewage

%

Positive

Y6

Number of days with good air quality

——

Positive

Y7

Area of public green space per caipta

m2/person

Positive

Y8

Greenery coverage in built-up areas

%

Positive

Y9

Forest coverage rate

%

Positive