Identification and Identifiability of non-linear IV/GMM Estimators

In this article, the identi¯cation of instrumental variables and generalised method of moment (GMM) estimators is discussed. It is common that representations of such models are derived from the solution to linear quadratic optimisation problems. Here, it is shown that even though the rank condition on the Jacobian and the instrument set is valid, that the transversality condition may not be satis¯ed by the estimated model. Further, acceptance of the transversality condition does occur when identi ¯cation fails or the forward model vanishes. As a result the parameters of such models irrespective of any correction for serial correlation may not be identi¯ed in a fundamental sense. This suggests that either forward looking models should be estimated directly or more complex non-linear restrictions should be imposed

Identifying and Solving Multivariate Rational Expectations Models (Updated: 01/2005)

This article discuses the identification of Generalised Rational Expectations Models. It is shown that the necessary and sufficient conditions for local identification of the Quasi-Structural Form (Q-SF) derive from the first derivatives of the Non-Linear Instrumental Variables (NLIV) criterion. The necessary and sufficient conditions for local identification consist of an appropriately defined and informative instrument set and a Jacobian matrix with appropriate rank. However, these conditions do not identify the full structural form (SF) linked to either the true expectations or the full solution. For the identification of SF, the parameters need to be associated with a model that satisfies the transversality condition. It is shown that the testing of this condition is impossible when relying exclusively on the existing instruments

Identifying asymmetric, multi-period Euler equations estimated by non-linear IV/GMM

In this article, the identification of instrumental variables and generalized method of moment (GMM) estimators with multi-period perceptions is discussed. The state space representation delivers a conventional first order condition that is solved for expectations when the Generalized Bézout Theorem holds. Here, it is shown that although weak instruments may be enough to identify the parameters of a linearized version of the Quasi-Reduced Form (Q-RF), their existence is not sufficient for the identification of the structural model. Necessary and sufficient conditions for local identification of the Quasi-Structural Form (Q-SF) derive from the product of the data moments and the Jacobian. Satisfaction of the moment condition alone is only necessary for local and global identification of the Q-SF parameters. While the conditions necessary and sufficient for local identification of the Q-SF parameters are only necessary to identify the expectational model that satisfies the regular solution. If the conditions required for the decomposition associated with the Generalized Bézout Theorem are not satisfied, then limited information estimates of the Q-SF are not consistent with the full solution. The Structural Form (SF) is not identified in the fundamental sense that the Q-SF parameters are not based on a forward looking expectational model. This suggests that expectations are derived from a forward looking model or survey data used to replace estimated expectations

Most UK scientists who publish extremely highly-cited papers do not secure funding from major public and charity funders: A descriptive analysis

The UK is one of the largest funders of health research in the world, but little is known about how health funding is spent. Our study explores whether major UK public and charitable health research funders support the research of UK-based scientists producing the most highly-cited research. To address this question, we searched for UK-based authors of peer-reviewed papers that were published between January 2006 and February 2018 and received over 1000 citations in Scopus. We explored whether these authors have held a grant from the National Institute for Health Research (NIHR), the Medical Research Council (MRC) and the Wellcome Trust and compared the results with UK-based researchers who serve currently on the boards of these bodies. From the 1,370 papers relevant to medical, biomedical, life and health sciences with more than 1000 citations in the period examined, we identified 223 individuals from a UK institution at the time of publication who were either first/last or single authors. Of those, 164 are still in UK academic institutions, while 59 are not currently in UK academia (have left the country, are retired, or work in other sectors). Of the 164 individuals, only 59 (36%; 95% CI: 29-43%) currently hold an active grant from one of the three funders. Only 79 (48%; 95% CI: 41-56%) have held an active grant from any of the three funders between 2006-2017. Conversely, 457 of the 664 board members of MRC, Wellcome Trust, and NIHR (69%; 95% CI: 65-72%) have held an active grant in the same period by any of these funders. Only 7 out of 655 board members (1.1%) were first, last or single authors of an extremely highly-cited paper. There are many reasons why the majority of the most influential UK authors do not hold a grant from the country’s major public and charitable funding bodies. Nevertheless, the results are worrisome and subscribe to similar patterns shown in the US. We discuss possible implications and suggest ways forward

Measuring consumer detriment under conditions of imperfect information

Copyright @ 2001 Office of Fair Tradin

xPF: Packet Filtering for Low-Cost Network Monitoring

The ever-increasing complexity in network infrastructures is making critical the demand for network monitoring tools. While the majority of network operators rely on low-cost open-source tools based on commodity hardware and operating systems, the increasing link speeds and complexity of network monitoring applications have revealed inefficiencies in the existing software organization, which may prohibit the use of such tools in high-speed networks. Although several new architectures have been proposed to address these problems, they require significant effort in re-engineering the existing body of applications. We present an alternative approach that addresses the primary sources of inefficiency without significantly altering the software structure. Specifically, we enhance the computational model of the Berkeley packet filter (BPF) to move much of the processing associated with monitoring into the kernel, thereby removing the overhead associated with context switching between kernel and applications. The resulting packet filter, called xPF, allows new tools to be more efficiently implemented and existing tools to be easily optimized for high-speed networks. We present the design and implementation of xPF as well as several example applications that demonstrate the efficiency of our approach

Kepler-210: An active star with at least two planets

We report the detection and characterization of two short-period, Neptune-sized planets around the active host star Kepler-210. The host star's parameters derived from those planets are (a) mutually inconsistent and (b) do not conform to the expected host star parameters. We furthermore report the detection of transit timing variations (TTVs) in the O-C diagrams for both planets. We explore various scenarios that explain and resolve those discrepancies. A simple scenario consistent with all data appears to be one that attributes substantial eccentricities to the inner short-period planets and that interprets the TTVs as due to the action of another, somewhat longer period planet. To substantiate our suggestions, we present the results of N-body simulations that modeled the TTVs and that checked the stability of the Kepler-210 system.Comment: 8 pages, 8 Encapsulated Postscript figure

Energy Supply Sustainability For Island Nations: A Study on 8 Global Islands

Energy supply sustainability is a multifaceted challenge for all countries and especially for small island nations that might have limited adaptive capacity. Previous studies showed that islands experience energy scarcity and isolation from energy markets due to their remote location. Our focus is on a range of islands spread out globally: Malta, Cyprus, Curacao, Mauritius, Iceland, Jamaica, Trinidad and Tobago and Bahrain. They are selected for their varying energy development paradigms that facilitate cluster elicitation. For the first time, we combine the estimation of fuel mix diversity and energy import dependence with established metrics Shannon-Wiener index (SWI), Herfindahl-Hirschman index (HHI) and Energy Import Dependence to assess energy supply security. SWI and Energy Import Dependence are then presented against carbon intensity to highlight two angles of sustainable energy supply. We argue that islands are clustered to those that have fossil fuel reserves and are locked in low diversity, low dependence and high carbon intensity, those that rely almost exclusively on imported fossil fuel reserves and have low diversity and high dependence and high carbon intensity and finally those that have entered a decarbonization trajectory that allows them to reduce their fossil fuel import dependence, increase their diversity and reduce their carbon intensity

Energy Supply Security in Southern Europe and Ireland

Energy supply security is of paramount importance to all countries, however, not all countries present the same capacity to respond to energy security threats. Financial wealth is one of the means that can support access to energy resources and as such countries that have been hit the hardest by the 2008 financial crisis present energy supply vulnerabilities. We focus on Ireland, Portugal, Spain, Italy and Greece and find that they have continuously improved their energy supply diversity. At the same time, we argue that during, and as a result of the financial crisis our focus countries reduced their exposure to expensive imported resources predominantly in the transport sector and increased the role of renewables. Overall, we find improved supply security which could be strengthened further if financial resources were directed towards innovation for renewable energy sources