| Variable | Notation | Unit of measure |
| Per capita carbon dioxide emission | CO2 | Metric tons |
| Per capita gross domestic product in real terms | GDP | US dollars |
| Per capita energy use | EN | Kilograms (of oil equivalent per capita) |
| Trade openness (share of trade in GDP) | OPEN | percent |
| Urbanization (share of urban population in total population) | UR | percent |
| Foreign direct investment (share in GDP) | FDI | percent |