Table 1. Standards of categorization and reference categories for socio-demographic measurements.
Characteristics | Level 1 | Level 2 | Level 3 | Level 4 | Level 5 |
Age | 0–14 | 14–60* | >60 | — | — |
Race | White* | black | American Indian | Asian | Other races |
Education attainment (years) | 0–4 | 5–8 | 9–12 | >12* | — |
Income (US$) | <19000 | > = 19000** | — | — | — |
*Reference category for comparison based on existing studies in the environmental justice literature.
**The classification standard for income is detailed in the text.