Mean 1990 SO2 concentration
Logarithm of real per capita GDP (PWT 5.6)
Square of inc
100*(Imports + Exports)/GDP  (PWT 5.6)
Index of democratic (+10) vs. autocratic (-10) institutions
lograithm of land area per capita
FR instrument for trade openness
FR instrument for income
FR instrument for square of income
country name
One for OECD country; otherwise zero