A country is on the carbon efficiency frontier if its per-capita emissions of CO2 are at least as low as any state that was at least as economically developed at a period when technology was no more advanced. Building on earlier work employing Data Envelopment Analysis to benchmark performance, we argue that a useful measure of whether a state adopts “good practice” in relation to climate change is how near it is to this frontier. We calculate efficiency scores for a sample of developed countries between 1994 and 2011, and model the impact of green taxation, next to a series of political and economic controls, on performance. We find that higher levels of environmental tax revenue are positively and significantly associated with higher carbon efficiency. The central contributions of this research are the introduction of an innovative measure for environmental quality and assessing how this is driven by green taxation.