Text and Data Mining valid from 2019-03-20
Received: 5 September 2018
Accepted: 12 February 2019
First Online: 20 March 2019
Ethics approval and consent to participate
: There are no ethical issues related to the analysis and publication of this paper as no people participate in the study which includes solely statistical analyses.
: Herewith, I confirm my agreement on publication of this paper in Energy, Sustainability and Society. I am the main and sole author of this paper.
: The author declares that he has no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.