Beyond Income: Energy Intensity, Industrialization and the CO₂ Environmental Kuznets Curve in 128 Countries (1990–2022)

Testing the environmental Kuznets curve hypothesis across the U.S.: Evidence from panel mean group estimators

There are growing concerns about environmental degradation and economic expansions in West Africa. Although there are several growth-environmental studies in Africa, there is limited empirical research exploring West African countries’ potential of benefiting from the environmental Kuznets curve (EKC) hypothesis, with the few studies on this subject reporting diverse results based on selected West African countries. To fill this gap, this study explored the relationship between economic growth and environmental degradation within the EKC framework using 16 West African countries sub-grouped into low-income countries (LICs) and lower-middle-income countries (LMICs) between 1990 and 2018. This study implemented second-generation panel econometric estimators that are robust to cross-sectional dependent and parameter heterogeneity. The empirical results revealed that the data is cross-sectionally dependent, heterogeneous, integrated of order one, 1(1), and cointegrated. Controlling for other environmental determinants, panel estimates from the Augmented Meant Group and Common Correlated Effect Mean Group estimators revealed that economic growth accelerates environmental degradation in West African countries, with a greater impact on LMICs, followed by LICs in West Africa. The results also showed that West African countries especially LMICs could benefit from the EKC hypothesis. On the other hand, growth-environmental degradation among LICs in West Africa shows a monotonous increasing relationship. We found strong evidence to support for feedback hypothesis between economic growth and environmental degradation in LMICs, LICs, and West Africa as a whole. Based on the findings, policy recommendations that consider both LMICs and LICs and West Africa as a whole were offered to policymakers.Graphical abstract

Has the Environmental Kuznets Curve hypothesis become stronger? A comparative analysis for OECD countries and selected late-industrializing Asian economies.

Heterogeneity of pollution haven/halo hypothesis and Environmental Kuznets Curve hypothesis across development levels of Chinese provinces

Renewable energy and CO2 emissions in middle-income economies: The roles of FDI, innovation, and industrialization under the EKC

Research Question: What is the applicability of the Environmental Kuznets Curve (EKC) hypothesis in emerging East and South Asian countries? Do institutional quality, trade openness, renewable energy consumption, green finance, financial development, and their interaction influence carbon emissions? Motivation: A new assessment of green finance, institutional quality, financial development, and other relevant variables in shaping the EKC hypothesis is required. Idea: In the context of emerging Asian countries, it requires consideration of cross-sectional dependence (CSD) due to the high economic integration among East and South Asian countries. They shared residual interdependency and cross-sectional exposure to common shocks, such as oil shocks, global financial shocks, and supply chain disruptions; hence, a more nuanced and multidisciplinary approach is needed. Data: A panel dataset that ranges from 2000 to 2019 is employed for ten developing East and South Asian economies, including China, India, Pakistan, Bangladesh, Sri Lanka, Indonesia, Malaysia, Thailand, Vietnam, and the Philippines. Method/Tools: A series of panel analyses, including the CSD test, slope heterogeneity test, the 2nd generation panel unit root and cointegration tests, and CS-ARDL modelling, have been employed to address heterogeneity and cross-sectional dependence issues. Robustness tests using the Augmented Mean Group (AMG) and Common Correlated Effects Mean Group (CCEMG) estimators corroborate the findings, reinforcing the study's credibility and policy implications. Findings: Both the short- and long-run results consistently confirm the income-environmental degradation link, but the U-type EKC effect is absent. While green finance, trade openness, and financial development have insignificant impacts on carbon emissions, institutional quality and renewable energy consumption exhibit negative effects, highlighting their importance in curbing environmental degradation. More policy efforts are needed to promote investment in environmental financing, upgrade clean production technology, and enhance the decarbonization process. This study also identifies heterogeneity and crosssectional dependence on environmental policies among these nations. Contributions: Green finance and R&D investments in green technologies are inadequate. Efforts to promote carbon neutrality by redirecting financing towards the sustainable and renewable energy sectors are needed. These findings underscore the need for greater collaborative efforts among emerging Asian nations, particularly China, to safeguard the environment and achieve sustainable development.

The achievement of economic growth is equally important as environmental sustainability. Economic growth is considered capable of enhancing the overall welfare of society. However, there is a sacrifice stemming from economic growth in the form of negative external impacts. Therefore, the objective of this study is to examine the Environmental Kuznets Curve (EKC) hypothesis in Indonesia and India. The EKC hypothesis connects economic growth with CO2 emissions. The Autoregressive Distributed Lag (ARDL) model is employed to assess both the long-term and short-term impacts of economic growth on CO2 emissions in Indonesia and India. Additionally, the study seeks to comprehend the applicability of the Environmental Kuznets Curve (EKC) hypothesis in these countries over the period of 1965-2021. The research findings indicate that economic growth has a significant impact on CO2 emissions in the short term, but this influence is not sustained in the long term in Indonesia. In contrast, in India, economic growth does not exhibit a significant effect on CO2 emissions in the short term, but it does have a notable impact in the long term. This implies that Indonesia does not align with the Environmental Kuznets Curve (EKC) hypothesis in the long term, while India is anticipated to adhere to the EKC hypothesis in the future.

Global warming has become the main concern in the present world. This research takes a comprehensive look at the interconnections between tourism, gross domestic product (GDP), renewable energy, fossil fuels, education, trade, and carbon dioxide (CO2) emissions in the Arab Peninsula. Including these variables, the research also checks the environmental Kuznets curve (EKC) hypothesis by analyzing the top 10 tourist destinations from 1997 to 2019. Saudi Arabia, Qatar, the United Arab Emirates, Iran, Israel, Jordan, Bahrain, Oman, Lebanon, and Egypt round out the top 10 countries in Arab in terms of tourist arrivals. The paper uses a novel augmented mean group (AMG) model to explore the problems of slope heterogeneity (SH), cross-sectional dependence (CSD), and the combination of level and first-difference stationery. An association between these variables over time can be discovered using the Westerlund cointegration method. To certify the accuracy of the findings, the research used both the mean group (MG) and common correlated effects mean group (CCEMG). According to the research, the EKC does not exist in the most popular Middle Eastern travel destinations. This basically means that as money grows, environmental conditions will deteriorate. The findings show that tourism can help reduce environmental harm there. Indicators such as rising populations, increased energy consumption, and thriving economies all influence the rise of the environmental degradation level. Trade will also increase environmental deterioration. The only things that will help reduce CO2 emissions are tourism and renewable energy. Therefore, the MG and CCEMG results corroborate the AMG findings. Governments may push for the widespread use of refillable energy sources and the development of ecotourism. Therefore, policymakers in this country should rethink their tourism strategies and adopt one that places a premium on renewable energy sources and environmental protection.

In this paper, we investigate the validity of the environmental Kuznets curve (henceforth, EKC) hypothesis for 8 OECD countries. To this aim, we decompose the per capita GDP series into its increases and decreases and consider only increases by excluding decreases from the model. Therefore, this method may enable us to test the EKC hypothesis more accurately, in accordance with the original theory. Following decomposition, we apply the fixed-effect regression model with Driscoll-Kraay standard errors, and the common correlated effects mean group (CCEMG) estimator. Empirical findings indicate that while the undecomposed model with undecomposed per capita GDP series supports the EKC hypothesis for 4 out of 8 countries, the decomposed model with decomposed per capita GDP series does not do so for any country. Hence, these mixed results reveal a need to employ different alternative techniques, such as the data transformation/decomposition applied in this study, for testing the EKC hypothesis.

Analysing export quality and ecological footprint nexus: evidence from South Asian countries

This study investigates the impact of natural resource rents, ICT expenditures, and energy intensity on environmental degradation in ASEAN countries for 2001–2023, while also testing the Environmental Kuznets Curve (EKC) hypothesis. Ecological footprint per capita is employed as a comprehensive indicator of environmental pressure. The empirical methodology comprises cross-sectional dependence tests, second-generation unit root and Westerlund cointegration tests, and heterogeneous panel estimators including Augmented Mean Group (AMG) and Common Correlated Effects Mean Group (CCEMG). Method of Moments Quantile Regression (MMQR) is used to capture distributional heterogeneity, supplemented by Dumitrescu–Hurlin causality analysis. The results reveal that natural resource reliance and energy intensity significantly worsen environmental degradation, supporting the resource-curse and energy-dependence hypotheses. Conversely, ICT spending contributes to environmental improvement, suggesting the role of digitalization in fostering sustainability. The positive GDP and negative GDP² coefficients also validate the EKC hypothesis in ASEAN. The study emphasizes the need for resource-efficient growth, clean energy transition, and ICT-based environmental strategies to achieve sustainable development in the ASEAN region.

China is the largest total pollution emitter country on the globe and a vast literature has investigated the environmental Kuznets curve (EKC) hypothesis in China. Thus, we aim to review empirical studies on the testing of the EKC hypothesis using different pollution proxies and area samples in China. The EKC hypothesis can be validated by establishing an inverted U-shaped or an N-shaped relationship between pollution and economic growth. In this review of the Chinese literature, the validity of the EKC hypothesis is found more often than its absence. In comparison, a higher proportion of the studies validated the EKC hypothesis using global pollution proxies compared with local pollution proxies. Moreover, a greater percentage of the studies substantiated the EKC hypothesis using Chinese provincial and city-level data compared with aggregate national data. To validate these findings, we applied logistic regression, and the chance of the validity of the EKC hypothesis was found to be 5.08 times higher than the absence of the EKC if a study used a global pollution proxy. Moreover, the chance of the existence of the EKC hypothesis was found to be 4.46 times higher than the nonexistence of the EKC if a study used Chinese provincial, city, sectoral, or industrial data.

In recent time, the investigation of the state of environmental quality has largely been conducted with less attention on the situation of environment sustainability especially in different economic regimes (expansion and recession). In the current context, the role of income per capita, energy intensity, and urbanization in driving the ecological footprint of Turkey is examined in the framework of Environmental Kuznets Curve (EKC) hypothesis over the period of 1990-2015. Considering the potential evidence of regime switching, we employed the Threshold Autoregressive Model (TAR) method with a regime change threshold of 14.43505 per hectare per capita and found that the EKC hypothesis is valid for all the 4 models. Moreover, eight observations are below the threshold value in the first regime while fifteen observations are equal or higher than the threshold value in the second regime. With a threshold per capita income of 9340.1326 USD, the study found that Turkey begin to experience a decline in environmental degradation resulting from income growth in 2015. However, this desirable outcome was short-lived in 2018 because the per capita income slightly decreases to 9340.1326 USD. In addition, increases in energy intensity and urbanization level hamper environmental sustainability drive of the country. The frequency domain causality test further supports the nexus evidence among the implied variables. By virtue of observation, this study offers that the government should work toward achieving a sustainable growth in order to attain the country's environmental sustainability agenda.

OECD countries have encountered the challenges of improving the environmental sustainability while maintaining economic growth by not impairing employment. This study attempts to reexamine the environmental Kuznets curve (EKC) hypothesis by using ecological footprint as an indicator of environmental degradation. Besides, our study aims to test the validity of environmental Phillips curve (EPC) and role of clean energy on ecological footprint. Our data cover a panel of 36 OECD countries from 1995 to 2015. We adopt the second-generation panel unit root and cointegration test to account for the presence of cross-section dependence (CSD). Moreover, the long-run relationship is estimated using Common Correlated Effect Mean Group (CCEMG) and Augmented Mean Group (AMG) that are robust to CSD. Our findings reveal that the EKC hypothesis is not valid while EPC is confirmed in OECD countries. Though there is a trade-off between unemployment and environmental degradation in OECD countries, the development of new technologies, especially in the clean energy sector, could be a key factor contributing to sustainable growth and better environmental quality. Thus, it is recommended that OECD countries should focus on the development of innovative green technologies and strengthen the initiatives that promote renewable energy consumption.

Discerning the role of renewable energy and energy efficiency in finding the path to cleaner consumption and production patterns: New insights from developing economies