| Variable | Describe | Note |
| WTP | Willingness to pay of HH | No = 0 |
| Yes = 1 | ||
| Age | Age of head of HH | Continuous variable |
| Gender | Gender of head of HH | Male = 1 |
| Female = 0 | ||
| Nf | Size of HH | Continuous variable |
| Inc | Income of Interviewees | <7 million VND/month = 1 |
| 7 - 15 million VND/month = 2 | ||
| 15 - 25 million VND/month =3 | ||
| >25 million VND/month = 4 | ||
| Edu | Education level of head of HH | Under high school = 1 |
| High school = 2 | ||
| Collge = 3 | ||
| University/ above university = 4 | ||
| Cog | Probability to agree or disagree with the statement “people should sacrifice part of their income to protect the environment” | Yes = 1 |
| No = 0 | ||
| P | Bid | 50 thousand VND/month = 1 |
| 60 thousand VND/month = 2 | ||
| 70 thousand VND/month = 3 | ||
| 90 thousand VND/month = 4 |