“…Out of the 25 studies analyzed (including the present one), 15 of them (60%) use the same set of inputs: labor force, capital stock and energy consumption [34,39,40,42,44,[47][48][49][50][52][53][54]56,57,59]. Furthermore, out of these 15 studies, four consider only the GDP as an output [44,49,53,56], while the rest consider the GDP as a desirable output and GHG emissions as an undesirable output [34,39,40,42,47,48,50,52,54,57,59]. Within DEA country comparisons, efficiency is, therefore, usually measured as a minimization of the labor force, capital stock, and energy consumption (inputs) in order to maximize the GDP (desirable output) and minimize the GHG emissions (undesirable output).…”