On Some Characteristics of Gaussian Covariance Functions

The concepts of isotropy/anisotropy and separability/non‐separability of a covariance function are strictly related. If a covariance function is separable, it cannot be isotropic or geometrically anisotropic, except for the Gaussian covariance function, which is the only model both separable and isotropic. In this paper, some interesting results concerning the Gaussian covariance model and its properties related to isotropy and separability are given, and moreover, some examples are provided. Finally, a discussion on asymmetric models, with Gaussian marginals, is furnished and the strictly positive definiteness condition is discussed.     

Macroprudential policy in a currency union

Review of World Economics - The past 20 years in Europe have seen large swings in real and financial markets, and sudden stops of capital flows have exposed the fault lines of the European...     

Work,Care and Gender during the COVID-19 Crisis*

We explore the effects of the COVID-19 crisis and the associated restrictions to economic activity on paid and unpaid work for men and women in the United Kingdom. Using data from the COVID-19 supplement of Understanding Society, we find evidence that labour market outcomes of men and women were roughly equally affected at the extensive margin, as measured by the incidence of job loss or furloughing. But, if anything, women suffered smaller losses at the intensive margin, experiencing slightly smaller changes in hours and earnings. Within the household, women provided on average a larger share of increased childcare needs, but in an important share of households fathers became the primary childcare providers. These distributional consequences of the pandemic may be important to understand its inequality legacy over the longer term.     

Consumption volatility and financial openness

Economic theory predicts that the integration of financial markets lowers the volatility of consumption. In this article, we study long-term trends in the consumption volatility of the G7 countries. Using different measures of financial openness, we find evidence that greater financial openness has been associated with lower consumption volatility. However, volatility of consumption relative to output has not declined.     

Ökonomische Folgen eines Atomausstiegs in Deutschland

Nach der Atomkatastrophe in Fukushima hat die Bundesregierung beschlossen, bis Mitte Juni die Zukunft der Atomenergie in Deutschland zu überdenken. Dabei k?nnen unterschiedlich weitgehende Szenarien betrachtet werden. Sie reichen von einer Rücknahme der im letzten Herbst beschlossenen Laufzeitverl?ngerung bis hin zum vollkommenen Ausstieg aus der Kernkraft. Die Autoren vertreten grunds?tzlich die Auffassung, dass die wirtschaftlichen Folgen eines Atomausstiegs zu bew?ltigen sind. Mit einer Steigerung der Energiepreise muss allerdings gerechnet werden — wie deutlich diese ausf?llt, und welche Referenzwerte herangezogen werden müssen, h?ngt von vielen Faktoren ab.     

Optimal Portfolios with Bounded Capital at Risk

We consider some continuous-time Markowitz type portfolio problems that consist of maximizing expected terminal wealth under the constraint of an upper bound for the capital at risk. In a Black–Scholes setting we obtain closed-form explicit solutions and compare their form and implications to those of the classical continuous-time mean-variance problem. We also consider more general price processes that allow for larger fluctuations in the returns.     

The estimation of agricultural policy effects on soil erosion—An application for the bio-economic model MODAM

As agricultural policies affect land use, they have effects on the amount of soil erosion in agricultural regions through changes of the economic conditions of agricultural production. Prices of inputs and outputs, regulations and incentives can change, forcing or encouraging farmers to adopt new crop rotations. This paper shows how a bio-economic model can be used to describe and estimate the effects of policies on agricultural production and the risk of soil erosion at the example of a region in North-Eastern Germany. The model uses both an assessment tool that is based on a fuzzy-logic approach for the estimation of soil erosion risk of cropping practices, and a linear programming model, that simulates farmers’ economic behaviour under the assumption of gross margin maximisation being the main goal of farmers’ actions.The analysed policy options were both a targeted and an untargeted incentive programme for reduced tillage, and a restriction option where high erosive crops are not allowed on high erodible field types. The results show that policy changes can have an impact on soil erosion. Furthermore, soil conservation policies are shown to have different levels of efficiency in terms of reduced soil erosion related to the costs of the policy. In the case of this study, a restriction option was more efficient than the incentive options. The results of such simulations can serve as a decision support for the development of soil conservation policies and help to foresee the effects of general changes of agricultural policies.     

Testing time-homogeneity of rating transitions after origination of debt

When modelling rating transitions as continuous-time Markov processes, in practice, time-homogeneity is a common assumption, yet restrictive, in order to reduce the complexity of the model. This paper investigates whether rating transition probabilities change after the origination of debt. Accordingly, we develop a likelihood-ratio test for the hypothesis of time-homogeneity. The alternative is a step function of transition intensities. The test rejects time-homogeneity for rating transitions observed over 7 years in a real corporate portfolio. Especially 1-year transition probabilities increase over the first year after origination. This time effect suggests that banks should manage their credit portfolios with respect to the age of debt.