This paper attempts to examine whether the environmental Kuznets curve (EKC) hypothesis is supported in MENA countries. We use, a novel RAM (range-adjusted measure)-based global Malmquist-Luenberger productivity index, accounting for slacks of inputs as well as desirable and undesirable outputs, to evaluate and decompose “green” productivity growth rates into technical change, pure efficiency change and scale change. By employing a panel smooth transition regression (PSTR) model, we investigate the income elasticity of environmental performance with respect to the decomposition factors. Our empirical results show that there are double thresholds when technical change and scale change are taken as transition variables, then leading to an inverted N-shaped curve between income and environmental performance. A single threshold is found when pure efficiency change is considered as a transition variable, yielding to an inverted U-shaped curve. Thus, our research does not find support for the EKC hypothesis.

本文试图检验中东和北非国家是否支持环境库兹涅茨曲线（EKC）假设。我们使用基于RAM（范围调整后的度量值）的新型全球Malmquist-Luenberger生产率指数（考虑到输入和期望与不期望的输出的不足）来评估“绿色”生产率增长率并将其分解为技术变化和纯效率变化和规模变化。通过采用面板平滑过渡回归（PSTR）模型，我们研究了环境绩效相对于分解因子的收入弹性。我们的经验结果表明，当将技术变化和规模变化作为过渡变量时，存在双重阈值，从而导致收入和环境绩效之间呈倒N型曲线。当将纯效率变化视为过渡变量时，会发现一个阈值，从而产生倒U形曲线。因此，我们的研究没有发现对EKC假设的支持。