• Initiative -
  • 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

Research Fellow Fakhri is a research fellow leading the KAPSARC Global Energy Macroeconometric Model (KGEMM) project. Previously, he was an associate professor… Fakhri is a research fellow leading the KAPSARC Global Energy Macroeconometric Model (KGEMM) project. Previously, he was an associate professor and director of the Center for Socio-Economic Research at Qafqaz University, Azerbaijan. He has served as a deputy director of the Research Institute at the Ministry of Economic Development, and a senior economist at the Research Department of the Central Bank of Azerbaijan Republic. He received a Fulbright Post-Doctoral Scholarship and conducted a research on building and applying a macroeconometric model for policy analysis at the George Washington University. Fakhri is a member of the research program on forecasting at the George Washington University and the editorial board of the Asian Journal of Business and Management Sciences. His research interests and experience span econometric modeling and forecasting, building and applying macroeconometric models for policy purposes, energy economics with a particular focus on natural resource-rich countries.

Expertise

  • Applied macroeconometrics
  • Energy economics
  • Time series modeling and forecasting

Publications See all Fakhri Hasanov’s publications

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

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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