Table 2:

Statistics description of samples

Variables	All samples (n=6630)		Urban samples (n=2700)		Rural samples (n=3930)
	Means	Standard deviation	Means	Standard deviation	Means	Standard deviation
CES-D scores	8.09	5.86	7.08	5.37	8.79	6.08
Psychological disorder	0.278	0.45	0.22	0.414	0.317	0.465
Urban-rural	0.41	0.49
SO2 drainage	6.63	7.4	7.04	6.56	6.34	7.91
Square of SO2 drainage	98.78	337.07	92.79	266.62	102.9	377.92
Age	67.66	6.35	67.78	6.55	67.56	6.21
Gender	0.52	0.499	0.5	0.5	0.53	0.499
Marriage	0.84	0.43	0.84	0.425	0.84	0.436
Primary school	0.46	0.49	0.43	0.496	0.48	0.5
Middle school	0.16	0.37	0.24	0.427	0.11	0.32
Vocational education, junior college and above	0.05	0.22	0.11	0.309	0.01	0.114
Physical disability	0.15	0.36	0.15	0.358	0.15	0.36
Social activity	0.55	0.497	0.62	0.484	0.51	0.5
Smoking	0.46	0.498	0.43	0.496	0.48	0.5
Drinking	0.41	0.49	0.39	0.488	0.41	0.493
Chronic disease 1	0.67	0.467	0.68	0.464	0.67	0.47
Chronic disease 2	0.41	0.407	0.23	0.421	0.19	0.397
Assets	7.6	47.04	13.9	71.55	3.33	13.04
Employment	0.49	0.49	0.28	0.451	0.63	0.483