The indicator measures the status of CO2 emissions while accounting for differences in national population and different paths of economic development. Countries are assessed according to the Environmental Kuznets Curve (EKC), which indicates that the relationship between per capita CO2 emissions and per capita GDP is positive only up to a certain point of development, after which the relationship becomes negative. A +/- 50 percent interval is created for the EKC, and a trend is measured for each country from 1990 to 2002. If a country's trend is greater than the +50 percent band, the country scores 0. If a country's trend is less than the band, it scores 1.