Pollution Emissions Issue Category consists of 2 indicators:

1) The SO2 growth rate, calculated as the average annual rate of increase or decrease in SO2 over the years 2005-2014. It is then adjusted for economic trends to isolate change due to policy rather than economic fluctuation. First, the EPI team calculates Spearman's correlation coefficient between SO2 emissions and GDP over a ten-year period. Second, they regress logged SO2 emissions over ten years to find a slope. Third, they calculate an unadjusted average annual growth rate in SO2 emissions. Fourth, they adjust the negative growth rates by a factor of 1 - the correlation coefficient.

2) The NOX growth rate, calculated as the average annual rate of increase or decrease in NOX over the years 2005-2014. It is then adjusted for economic trends to isolate change due to policy rather than economic fluctuation. First, the EPI team calculates Spearman's correlation coefficient between NOX emissions and GDP over a ten-year period. Second, they regress logged NOX emissions over ten years to find a slope. Third, they calculate an unadjusted average annual growth rate in NOX emissions. Fourth, they adjust the negative growth rates by a factor of 1 - the correlation coefficient.

Both indicators are given equal weight in the aggregation. The issue category varies from 0 to 100.