Table 1.

Demographic characteristics of participants.

	Group	Freq.	Percent%
Gender	Male	1869	49.42
	Female	1913	50.58
Hukou	Rural	2266	59.92
	City	1516	40.08
Ethnicity	Han Nationality	3539	93.57
	Else	243	6.43
Education	Illiterate	870	23
	Else	2912	77
Marriage	In marriage	2743	72.53
	Else	1039	27.47