Table 2 Descriptive statistics of main variables

ADL disability

1 ~ 5; higher score indicated lower ADL disability

4.651

0.513

4.636

0.595

SO₂

SO₂ content in air (μg /m³)

27.53

17.96

16.26

10.58

NO₂

NO₂ content in air (μg /m³)

32.74

11.62

39.23

15.93

PM₁₀

PM₁₀ content in air (μg /m³)

94.38

40.94

89.74

40.32

AQI

Dimensionless air quality; greater value indicated poorer quality

85.76

25.79

72.14

16.55

Fiscal expenditure

Total annual financial expenditure of the region (million yuan)

544.9

729.6

688.0

1030

Sunshine duration

Total sunshine duration in the whole year, (hour)

1814

469.0

1903

354.4

Rainfall

Annual total rainfall (mm)

1067

624.8

997.3

441.2

Per capita GDP

Annual regional GDP to population ratio, (yuan / person)

49,467

34,418

56,468

35,992

Population density

Annual area to population ratio (Person / m²)

490.1

479.4

492.6

473.1

Average temperature

Annual average temperature (centigrade)

15.24

3.867

15.08

3.926

GDP growth

Regional GDP growth compared with the previous year

8.078

2.081

7.054

1.823

Green space coverage

Ratio of green area to total area (in built up area)

39.54

9.130

39.96

5.022

Relative humidity

Percentage of water vapor pressure in air to saturated vapor pressure at the same temperature

64.65

12.39

65.03

10.64

Household register

Urban = 1, rural = 0

0.401

0.490

0.405

0.491

Income

1 ~ 5 respectively represent high income, middle-high-income, middle income, lower-middle-income and low income

2.605

0.783

2.754

0.803

Basic medical insurance

Enjoying basic medical insurance = 1, no = 0

0.945

0.137

0.971

0.168

Marital status

Widowed = 1, no = 0

0.103

0.304

0.125

0.330

Serious illness

Number of serious illnesses diagnosed; higher value indicates a greater number of illnesses

0.0294

0.286

0.724

1.052

Depression

1–4; higher score indicates more severe depression

2.468

0.740

2.275

0.783

Self-reported health

1 ~ 5; higher value indicates better health

2.955

0.721

2.946

0.986

Body disability

0–5; higher score indicates more severe body disability

0.154

0.444

0.145

0.445

Physical pain

1–5; higher score indicates more severe pain

1.705

0.456

2.159

1.267

Age

Actual age of the individual in the survey year

59.14

10.32

58.74

10.32

Gender

Male = 1, female = 0

0.478

0.500

0.474

0.499

Education level

1–11 respectively represent No formal education (illiterate),Did not finish primary school, Sishu/home school, Elementary school, Middle school, High school, Vocational school, Two−/Three-Year College/Associate degree, Four-Year College/Bachelor’s degree, Master’s degree, Doctoral degree/Ph.D.

3.390

1.001

3.477

1.935