Exploring the Environmental Kuznets Hypothesis. Theoretical and Econometric Problems

Focussing on the prime example of CO2 emissions, we discuss several important theoretical and econometric problems that arise when studying environmental Kuznets curves (EKCs). The dominant theoretical approach is given by integrated assessment modelling, which consists of economic models that are combined with environmental impact models. We critically evaluate the aggregation, model dynamics and calibration aspects and their implications for the validity of the results. We then turn to a discussion of several important econometric problems that go almost unnoticed in the literature. The most fundamental problems relate to nonlinear transformations of nonstationary regressors and, in a nonstationary panel context, to neglected cross–sectional dependence. We discuss the implications of these two major and some minor problems that arise in the econometric analysis of Kuznets curves. Our discussion shows that EKC modelling as performed to date is subject to major drawbacks at both the theoretical and the econometric level.Carbon Kuznets curve, Integrated assessment models, Regressions with integrated variables, Nonstationary panels

The Carbon Kuznets Curve: A Cloudy Picture Emitted by Bad Econometrics?

In this paper we discuss three important econometric problems with the estimation of Environmental Kuznets Curves, which we exemplify with the particular example of the Carbon Kuznets Curve (CKC). The Carbon Kuznets hypothesis postulates an inverse U-shaped relationship between per capita GDP and per capita CO2 emissions. All three problems occur in the presence of unit root nonstationary regressors in panels. Two of them are rather fundamental: First, the use of nonlinear transformations of integrated regressors in the Kuznets curve, which usually contains GDP and its square is problematic. This stems from the fact that nonlinear transformations of integrated processes are in general not integrated, which implies that (panel) unit root and cointegration techniques, widely used by now in the Kuznets curve literature, cannot be applied meaningfully in this context. Second, all methods applied up to now rest upon the assumption of cross-sectional independence. With a first application of factor model based methods that allow for cross-sectional dependence, we find evidence for nonstationary common factors in both the GDP and CO2 emissions series. Estimating the CKC on stationary de-factored data, we do not find support for an inverse U-shape. The third problem, abstaining at this point from the above two fundamental problems, is that the unit root and cointegration methods have been used too uncritically. In particular the notorious small sample problems of unit root and cointegration problems have been neglected. By applying various bootstrap algorithms and several estimators we show that a careful analysis should have lead researchers to interpret their results with more caution than commonly done, even when being unaware of the two problems stated aboveCarbon Kuznets Curve; panel data; unit roots; cointegration; cross-sectional dependence; nonlinear transformations of regressors

Incidence and Growth of Patent Thickets - The Impact of Technological Opportunities and Complexity

We investigate incidence and evolution of patent thickets. Our empirical analysis is based on a theoretical model of patenting in complex and discrete technologies. The model captures how competition for patent portfolios and complementarity of patents affect patenting incentives. We show that lower technological opportunities increase patenting incentives in complex technologies while they decrease incentives in discrete technologies. Also, more competitors increase patenting incentives in complex technologies and reduce them in discrete technologies. To test these predictions a new measure of the density of patent thickets is introduced. European patent citations are used to construct measures of fragmentation and technological opportunity. Our empirical analysis is based on a panel capturing patenting behavior of 2074 firms in 30 technology areas over 15 years. GMM estimation results confirm the predictions of our theoretical model. The results show that patent thickets exist in 9 out of 30 technology areas. We find that decreased technological opportunities are a surprisingly strong driver of patent thicket growth

Zur Verbreitung von Cyperus fuscus L. in Westniedersachsen

Cyperus fuscus L., das braune Cypergras, ist eine einjährige Nanocyperion-Art, die in den vergangenen 40 Jahren in Westniedersachsen sehr selten geworden ist. Ihre aktuelle Verbreitung in diesem Gebiet und ein neuer Standort werden dargestellt

How to measure patent thickets – a novel approach

The existing literature identifies patent thickets indirectly. In this paper we propose a novel measure based on patent citations which allows us to measure the density of patent thickets directly. We discuss the algorithm which generates the measure and present descriptive results validating it. Moreover, we identify technology areas which are particularly impacted by patent thickets.patenting; patent thickets; patent portfolio races; complexity

Ergänzungen zur Flora von Südwest-Niedersachsen und dem benachbarten Westfalen : Taraxacum lacistophyllum (Dahlst.) Raunk. und Taraxacum subundulatum Dahlst. ; Herrn Prof. Dr. Dr. H. E. Weber in großer Dankbarkeit zum 65. Geburtstag gewidmet

Zwei in Südwestniedersachsen erstmals beobachtete Taraxacum-Arten, T. lacistophyllum und T. subundulatum, werden vorgestellt.For the first time, two species of the genus Taraxacum, T. lacistophyllum and T. subundulatum have been found in the southwest of Lower Saxony. They are shown in a short presentation

Erste Übersicht über die Armleuchteralgen (Characeae) des Raumes Osnabrück

Aus Anlaß des Wiederfundes von Chara contraria A. Sr., die zületzt 1897 in Niedersachsen festgestellt worden war, werden die derzeit bekannten Arten der Armleuchteralgen (Characeae) und ihre Verbreitung im Raum Osnabrück vorgestellt. Ein Sestimmungsschlüssel ist beigegeben.On the occasion of the rediscovery of Chara contraria A. Sr., which was found for the last time in 1897 in Lower Saxony, the known species of the Characeae and their distribution in the area of Osnabrück (Lower Saxony, Germany) is shown. A key to the species is enclosed