The trade-off between scope and precision in sustainability assessments of food systems

With sustainability becoming an increasingly important issue, several tools have been developed, promising to assess sustainability of farms and farming systems. However, looking closer at the scope, the level of assessment and the precision of indicators used for impact assessment we discern considerable differences between the sustainability impact assessment tools at hand. The aim of this paper is therefore to classify and analyse six different sustainability impact assessment tools with respect to the assessment level, the scope and the precision. From our analysis we can conclude that there is a trade-off between scope and precision of these tools. Thus one-size-fits-all solutions with respect to tool selection are rarely feasible. Furthermore, as the indicator selection determines the assessment results, different and inconsistent indicators could lead to contradicting and not comparable assessment results. To overcome this shortcoming, sustainability impact assessments should disclose the methodological approach as well as the indictor sets use and aim for harmonisation of assumptions

Reducing the Excess Burden of Subsidizing the Stork: Joint Taxation, Individual Taxation, and Family Tax Splitting

Analyzing a homogenous household setting with endogenous fertility and endogenous labor supply, we demonstrate that moving from joint taxation to individual taxation and adapting child benefits so as to keep fertility constant entails a Pareto improvement. The change is associated with an increase in labor supply and consumption and a reduction of the marginal income tax, while the child benefit may move in either direction. Similarly, a move from joint taxation to some scheme of family tax splitting increases labor supply and welfare.income taxation, fertility, splitting, labor supply

Pension, Fertility, and Education

A pay-as-you-go pension scheme is associated with positive externalities of having children and providing them with human capital. In a framework with heterogeneity in productivity, and stochastic and endogenous investment in fertility and education, we discuss internalization policies associated with child benefits in the pension formula. The second-best scheme displays both a benefit contingent on the contributions of children and a purely fertility-related component.pay-as-you-go, fertility, human capital, externalities

Ökobilanzen vorerst nur bedingt aussagekräftig

Zunehmend werden Ökobilanzen herangezogen, um die Umweltwirkungen der landwirtschaftlichen Produktion zu beurteilen. Auch zum Vergleich der Auswirkungen verschiedener Landwirtschaftssysteme setzt man die Methodik ein. Das Instrument der Ökobilanzierung ist aber nicht fertig entwickelt, die heutigen Anwendungen können zu Trugschlüssen führen

Simulating evolutionary responses of an introgressed insect resistance trait for ecological effect assessment of transgene flow: a model for supporting informed decisionmaking in environmental risk assessment

Predicting outcomes of transgene flow from arable crops requires a system perspective that considers ecological and evolutionary processes within a landscape context. In Europe, the arable weed Raphanus raphanistrum is a potential hybridization partner of oilseed rape, and the two species are ecologically linked through the common herbivores Meligethes spp. Observations in Switzerland show that high densities of Meligethes beetles maintained by oilseed rape crops can lead to considerable damage on R. raphanistrum. We asked how increased insect resistance in R. raphanistrum – as might be acquired through introgression from transgenic oilseed rape – would affect seed production under natural herbivore pressure. In simulation experiments, plants protected against Meligethes beetles produced about twice as many seeds as unprotected plants. All stages in the development of reproductive structures from buds to pods were negatively affected by the herbivore, with the transition from buds to flowers being the most vulnerable. We conclude that resistance to Meligethes beetles could confer a considerable selective advantage upon R. raphanistrum in regions where oilseed rape is widely grown

Evaluating On-Farm Biodiversity: A Comparison of Assessment Methods

Strategies to stop the loss of biodiversity in agriculture areas will be more successful if farmers have the means to understand changes in biodiversity on their farms and to assess the effectiveness of biodiversity promoting measures. There are several methods to assess on-farm biodiversity but it may be difficult to select the most appropriate method for a farmer’s individual circumstances. This study aims to evaluate the usability and usefulness of four biodiversity assessment methods that are available to farmers in Switzerland. All four methods were applied to five case study farms, which were ranked according to the results. None of the methods were able to provide an exact statement on the current biodiversity status of the farms, but each method could provide an indication, or approximation, of one or more aspects of biodiversity. However, the results also showed that it is possible to generate different statements on the state of biodiversity on the same farms by using different biodiversity assessment methods. All methods showed strengths and weaknesses so, when choosing a method, the purpose of the biodiversity assessment should be kept in the foreground and the limitations of the chosen methods should be considered when interpreting the outcomes

Pairing gaps near ferromagnetic quantum critical points

We address the quantum-critical behavior of a two-dimensional itinerant ferromagnetic systems described by a spin-fermion model in which fermions interact with close to critical bosonic modes. We consider Heisenberg ferromagnets, Ising ferromagnets, and the Ising nematic transition. Mean-field theory close to the quantum critical point predicts a superconducting gap with spin-triplet symmetry for the ferromagnetic systems and a singlet gap for the nematic scenario. Studying fluctuations in this ordered phase using a nonlinear sigma model, we find that these fluctuations are not suppressed by any small parameter. As a result, we find that a superconducting quasi-long-range order is still possible in the Ising-like models but long-range order is destroyed in Heisenberg ferromagnets.Comment: 13 pages, 7 figure

Essays in Macroeconomics and Macroeconometrics

This thesis contributes to macroeconomics and macroeconometrics. Chapters 2-4 study the role of producer heterogeneity for business cycles and macroeconomic development. Chapters 5-6 provide inference for structural vector autoregressions. Chapter 2 examines the role of time to build for business cycles. We document that time to build is volatile and largest during recessions. In a model with producer heterogeneity and capital adjustment frictions, the longer time to build, the less frequently firms invest, and the less firm investment reflects firm productivity. Longer time to build thus worsens the allocation of capital across firm. In the calibrated model, one month longer time to build lowers GDP by 0.5%. Chapter 3 investigates the role of uncertainty fluctuations. We exploit highly disaggregated industry-level data to study the empirical importance of various transmission channels of uncertainty shocks. We provide testable implications for the interaction between various frictions and the job flow responses to uncertainty shocks. Empirically, uncertainty shocks lower job creation and raise job destruction in more than 80% of industries. In line with theory, these responses are significantly magnified by the severity of financial frictions. In contrast, we do not find supportive evidence for other transmission channels. Chapter 4 re-examines the importance of misallocation for macroeconomic development. We ask whether differences in micro-level factor productivities should be understood as a result of frictions in technology choice. We document that the bulk of all productivity differences is persistent and related to highly persistent differences in the capital-labor ratio. This suggests a cost of adjusting this ratio. In fact, a model with such friction can explain our findings. At the same time, the loss in productive efficiency from this friction is modest. Chapter 5 studies structural VAR models that impose equality and/or inequality restrictions on a single shock, e.g. a monetary policy shock. The paper proposes a computationally convenient algorithm to evaluate the smallest and largest feasible value of the structural impulse response. We further show under which conditions these values are directionally differentiable and propose delta-method inference for the set-identified structural impulse response. We apply our method to set-identify the effect of unconventional monetary policy shocks. In Chapter 6 we study models that impose restrictions on multiple shocks. The projection region is the collection of structural impulse responses compatible with the vectors of reduced-form parameters contained in a Wald ellipsoid. We show that the projection region has both frequentist coverage and robust Bayesian credibility. To address projection conservatism, we propose a feasible calibration algorithm, which achieves exact robust Bayesian credibility of the desired credibility level, and, additionally, exact frequentist coverage under differentiability assumptions

A hit-and-run Giant Impact scenario

The formation of the Moon from the debris of a slow and grazing giant impact of a Mars-sized impactor on the proto-Earth (Cameron & Ward 1976, Canup & Asphaug 2001) is widely accepted today. We present an alternative scenario with a hit-and-run collision (Asphaug 2010) with a fractionally increased impact velocity and a steeper impact angle.Comment: 11 pages, 2 figures, in press in ICARUS note

Theory of filtered type-II PDC in the continuous-variable domain: Quantifying the impacts of filtering

Parametric down-conversion (PDC) forms one of the basic building blocks for quantum optical experiments. However, the intrinsic multimode spectral-temporal structure of pulsed PDC often poses a severe hindrance for the direct implementation of the heralding of pure single-photon states or, for example, continuous-variable entanglement distillation experiments. To get rid of multimode effects narrowband frequency filtering is frequently applied to achieve a single-mode behavior. A rigorous theoretical description to accurately describe the effects of filtering on PDC, however, is still missing. To date, the theoretical models of filtered PDC are rooted in the discrete-variable domain and only account for filtering in the low gain regime, where only a few photon pairs are emitted at any single point in time. In this paper we extend these theoretical descriptions and put forward a simple model, which is able to accurately describe the effects of filtering on PDC in the continuous-variable domain. This developed straightforward theoretical framework enables us to accurately quantify the trade-off between suppression of higher-order modes, reduced purity and lowered Einstein-Podolsky-Rosen (EPR) entanglement, when narrowband filters are applied to multimode type-II PDC.Comment: 15 pages, 13 figure