Estimating Different Order Polynomial Logarithmic Environmental Kuznets Curves

  • Focus Area -
  • Type KAPSARC journal article
  • Date 11 April 2021
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Abstract

This paper contributes to the environmental literature by (i) demonstrating that the estimated coefficients and the statistical significance of the non-leading terms in quadratic, cubic, and quartic logarithmic environmental Kuznets curve (EKC) specifications are arbitrary and should therefore not be used to choose the preferred specification and (ii) detailing a proposed general-to-specific type methodology for choosing the appropriate specifications when attempting to estimate higher-order polynomials such as cubic and quartic logarithmic EKC relationships. Testing for the existence and shape of the well-known EKC phenomenon is a hot topic in the environmental economics literature. The conventional approach widely employs quadratic and cubic specifications and more recently also the quartic specification, where the variables are in logarithmic form. However, it is important that researchers understand whether the estimated EKC coefficients, turning points, and elasticities are statistically acceptable, economically interpretable, and comparable. In addition, it is vital that researchers have a clear structured non-arbitrary methodology for determining the preferred specification and hence shape of the estimated EKC. We therefore show mathematically and empirically the arbitrary nature of estimated non-leading coefficients in quadratic, cubic, and quartic logarithmic EKC specifications, being dependent upon the units of measurement chosen for the independent variables (e.g. dependent upon a rescaling of the variables such as moving from $m to $bn). Consequently, the practice followed in many previously papers, whereby the estimates of the non-leading terms are used in the decision to choose the preferred specification of an estimated EKC relationship, is incorrect and should not be followed since it potentially could lead to misleading conclusions. Instead, it should be based upon the sign and statistical significance of the estimated coefficients of the leading terms, the location of turning point(s), and the sign and statistical significance of the estimated elasticities. Furthermore, we suggest that researchers should follow a proposed general-to-specific type methodology for choosing the appropriate order of polynomials when attempting to estimate higher-order polynomial logarithmic EKCs.

https://doi.org/10.1007/s11356-021-13463-y

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Authors

Fakhri Hasanov

Fakhri Hasanov

Senior Fellow I Fakhri Hasanov is a senior fellow and leads the KAPSARC Global Energy Macroeconometric Model projects with 20+ years of experience… Fakhri Hasanov is a senior fellow and leads the KAPSARC Global Energy Macroeconometric Model projects with 20+ years of experience in econometric modeling and forecasting. Since 2015, he has been involved in multistakeholder projects, leading and executing macroeconomic analysis of various policy choices and initiatives (e.g., energy prices, energy demand, and fiscal reforms) for the Kingdom’s economy. He has extensive experience working with policymakers. Prior to KAPSARC, he was a post-doc at George Washington University. His research mainly covers macro-econometric modeling for energy and environmental economics policy analyses. Dr. Hasanov has authored 50+ applied studies published in reputable journals such as Energy Policy, Energy Economics, Empirical Economics, and Energy Strategy Review. His research is recognized internationally (e.g., he is listed among the top 2% of scientists globally by Elsevier). Fakhri is an editorial board member of various peer-reviewed journals, such as Frontiers in Environmental Science. He holds a Ph.D. in econometrics.

Expertise

  • Econometric modeling and forecasting
  • Time series and panel data econometrics
  • Macroeconometric models for policy analyses
  • Energy economics
  • Environmental economics.

Publications See all Fakhri Hasanov’s publications

Jeyhun Mikayilov

Jeyhun Mikayilov

Research Fellow Jeyhun is a research fellow at KAPSARC. He received his B.A. and M.S. from Azerbaijan State University (now Baku State… Jeyhun is a research fellow at KAPSARC. He received his B.A. and M.S. from Azerbaijan State University (now Baku State University) in mathematics. Jeyhun holds a Ph.D. in applied mathematics and a D.S. in econometrics. Before joining KAPSARC in September 2017, Jeyhun was an associate professor at the Department of Statistics and Econometrics at Azerbaijan State University, and the Department of Economics at Qafqaz University, where he taught econometrics, statistics, and mathematical economics. His other roles have included director of the Research Institute for Social Sciences and Humanities, and head of the Center for Socio-Economic Research. Jeyhun was a postdoctoral researcher at Indiana University Bloomington, United States (U.S.). He has also been a visiting researcher at several institutions, including the Center for Econometric Research, Sungyunkwan University in Seoul, South Korea; Vistula University, Warsaw, Poland; the University of North Texas, and the University of South Texas, both in the U.S. Jeyhun’s research is focused on applied time series econometrics, the economics of energy, the environment and sustainable development. He has authored over 40 scientific articles published in peer-reviewed journals and is an editorial board member of the International Journal of Advanced Multidisciplinary Research and Review, the Journal of Management, Economics and Industrial Organization, and the Journal of Socio-Economic Studies, and a member of the International Association for Energy Economics.

Expertise

  • Applied Time Series Econometrics
  • The Economics of Energy and Environment
  • Sustainable Development

Publications See all Jeyhun Mikayilov’s publications

Lester C. Hunt

Lester C. Hunt

Visiting Researcher Lester C. Hunt is a part-time Professor of Economics at the University of Portsmouth and a KAPSARC Visiting Researcher. Lester… Lester C. Hunt is a part-time Professor of Economics at the University of Portsmouth and a KAPSARC Visiting Researcher. Lester previously worked at the Universities of Essex (1979-1980), Swansea (1980-1985 and 1987-1989), Surrey (1989-1991 and 1999-2017), and Portsmouth (1994-1998, and 2017 onwards). At Surrey he was Head of Economics (1999-2003) and Director of SEEC (2003-2015). At Portsmouth he was Head of Economics (1996 -1998) and Head of Economics and Finance (2017-2021). In addition to working in higher education, Lester was an Economic Adviser in the forecasting division of HM Treasury (1985-1987), an Energy Analyst/Economist at Midlands Electricity (1991-1994) and a Senior Research Fellow at KAPSARC (2015-2017). Lester holds a B.Sc. (Hons) in Economics with Econometrics from Loughborough University, an MA in Economics from the University of Essex, and a Ph.D. in Economics from the University of Surrey. He has been an Editor of The Energy Journal since 2006.

Expertise

  • Energy Economics and Policy

Publications See all Lester C. Hunt’s publications

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