Gender of the sample
1 = male
2 = female

Education level
1 = Vocational education
2 = Undergraduate education

Only child or not
1 = yes
2 = no

Type of residence
1 = Countryside
2 = City or town

Annual family income
1 = RMB 10,000 to 150,000
2 = RMB 150,000 to 300,000
3 = RMB 300,000 to 500,000
4 = RMB 500,000 to 1 million
5 = RMB 1,000,000 or more

0 = Not Selected
1 = Selected