The standard approach to the Environmental Kuznets Curve (EKC) holds that as a country develops and GDP per capita grows environmental degradation initially increases but eventually it reaches a turning point where environmental degradation begins to decline. Environmental degradation takes many forms, one of them being emissions of harmful gases. According to the EKC concept, a country can reduce emissions by ‘growing’. The standard approach implicitly assumes that a country emits as little as possible for its economic development, whereas in reality, a country might emit above the best attainable level of emissions. Therefore, emissions could be reduced before and after the turning point by becoming more environmentally efficient – i.e., ‘improving’ the emissions level. This article proposes a Stochastic Environmental Kuznets Frontier (SEKF) which is estimated for CO₂ emissions for OECD countries and used to benchmark each country before and after the turning point differently, thus, indicating how a country could ‘grow’ and/or ‘improve’ to reduce its CO₂ emissions. Additionally, we analyse the role of the stringency of environmental policies in reducing a country's carbon inefficiency measured by the distance from the benchmark EKC and find widespread carbon inefficiencies that could be reduced by more stringent market-based environmental policies.

环境库兹涅茨曲线 (EKC) 的标准方法认为，随着一个国家的发展和人均 GDP 的增长，环境退化最初会增加，但最终会达到环境退化开始下降的转折点。环境退化有多种形式，其中之一是有害气体的排放。根据EKC 概念，一个国家可以通过“增长”来减少排放。标准方法隐含地假设一个国家为了经济发展尽可能少地排放，而实际上，一个国家的排放量可能高于可达到的最佳排放水平。因此，可以通过提高环境效率（即“改善”排放水平）来减少转折点前后的排放量。₂ OECD 国家的排放量，用于在转折点之前和之后以不同方式对每个国家进行基准测试，从而表明一个国家如何“增长”和/或“改善”以减少其 CO 2 排放_量。此外，我们通过与基准 EKC 的距离来分析严格的环境政策在减少一个国家的碳效率低下方面的作用，并发现可以通过更严格的基于市场的环境政策来减少普遍存在的碳效率低下。