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In response to the COVID-19 pandemic, large parts of the economy were locked down and, as a result, households’ income risk rose sharply. At the same time, policy makers put forward the largest stimulus package in history. In the United States it amounted to $2 trillion, a quarter of which represented transfer payments to households. To the extent that such transfers were (i) announced in advance and (ii) conditional on recipients being unemployed, they mitigated income risk associated with the lockdown—in contrast to unconditional transfers. We develop a baseline scenario for a COVID-19 recession in a medium-scale heterogeneous agent new Keynesian model and use counterfactuals to quantify the impact of transfers. For the short run, we find large differences in the transfer multiplier: it is negligible for unconditional transfers and about unity for conditional transfers. Overall, we find that the transfers reduced the output loss due to the pandemic by some two percentage points at its trough.

Zusammenfassung Im Rahmen des deutschen Konjunkturpakets 2020 wurde eine temporäre Erhöhung des Kindergeldes, ein Kinderbonus, von 300 Euro pro kindergeldberechtigtem Kind beschlossen. Dieser Bonus wurde in zwei Raten ausgezahlt, eine im September (200 Euro) und eine im Oktober 2020 (100 Euro). Wir verwenden eine repräsentative Umfrage zum monatlichen Konsumverhalten deutscher Haushalte, um die intertemporale Konsumwirkung dieses Transfers zu schätzen. Gemäß diesen Schätzungen verausgaben die Kindergeldempfänger im Durchschnitt 28 bis 37 Prozent des Transfers als zusätzlichen Konsum bereits zwischen September und November 2020. Allerdings konzentriert sich die Ausgabensteigerung signifikant – wie auch theoretisch zu erwarten – auf Kindergeldempfänger mit niedrigem liquiden Vermögen, die erwarten, dass sie den Kinderbonus nicht vollständig über die Einkommensteuer zurückzahlen müssen. Diese Gruppe verausgabt den zusätzlichen Transfer fast vollständig.

Assistenzsysteme bieten die Möglichkeit, Werker bei manuellen Montageprozessen mit zahlreichen Varianten und Arbeitsinhalten zu unterstützen. Die Konfiguration eines bestehenden Assistenzsystems für neue Produktvarianten kann einen hohen Aufwand in der Arbeitsvorbereitung verursachen. Eine Darstellung des Status quo beim Anlegen neuer Produktvarianten fehlt allerdings bisher aufgrund der Neuartigkeit der Systeme. Daher werden der Konfigurationsprozess und die Herausforderungen anhand einer Literaturrecherche und durch Interviews strukturiert aufgearbeitet.

When approximating the expectations of a functional of a solution to a stochastic differential equation, the numerical performance of deterministic quadrature methods, such as sparse grid quadrature and quasi-Monte Carlo (QMC) methods, may critically depend on the regularity of the integrand. To overcome this issue and improve the regularity structure of the problem, we consider cases in which analytic smoothing (bias-free mollification) cannot be performed and introduce a novel numerical smoothing approach by combining a root-finding method with a one-dimensional numerical integration with respect to a single well-chosen variable. We prove that, under appropriate conditions, the resulting function of the remaining variables is highly smooth, potentially affording the improved efficiency of adaptive sparse grid quadrature (ASGQ) and QMC methods, particularly when combined with hierarchical transformations (ie., the Brownian bridge and Richardson extrapolation on the weak error). This approach facilitates the effective treatment of high dimensionality. Our study is motivated by option pricing problems, focusing on dynamics where the discretization of the asset price is necessary. Based on our analysis and numerical experiments, we demonstrate the advantages of combining numerical smoothing with the ASGQ and QMC methods over these methods without smoothing and the Monte Carlo approach. Finally, our approach is generic and can be applied to solve a broad class of problems, particularly approximating distribution functions, computing financial Greeks, and estimating risk quantities., Comment: arXiv admin note: substantial text overlap with arXiv:2003.05708

Least squares Monte Carlo methods are a popular numerical approximation method for solving stochastic control problems. Based on dynamic programming, their key feature is the approximation of the conditional expectation of future rewards by linear least squares regression. Hence, the choice of basis functions is crucial for the accuracy of the method. Earlier work by some of us [Belomestny, Schoenmakers, Spokoiny, Zharkynbay. Commun.~Math.~Sci., 18(1):109-121, 2020](arXiv:1808.02341) proposes to reinforce the basis functions in the case of optimal stopping problems by already computed value functions for later times, thereby considerably improving the accuracy with limited additional computational cost. We extend the reinforced regression method to a general class of stochastic control problems, while considerably improving the method's efficiency, as demonstrated by substantial numerical examples as well as theoretical analysis.

Metal-organic frameworks (MOFs) are commended as photocatalysts for H2 evolution and CO2 reduction as they combine light-harvesting and catalytic functions with excellent reactant adsorption capabilities. For dynamic processes in liquid phase, the accessibility of active sites becomes a critical parameter as reactant diffusion is limited by the inherently small micropores. Our strategy is to introduce additional mesopores by selectively removing one ligand in mixed-ligand MOFs via thermolysis. Here we report photoactive MOFs of the MIL-125-Ti family with two distinct mesopore architectures resembling either large cavities or branching fractures. The ligand removal is highly selective and follows a 2-step process tunable by temperature and time. The introduction of mesopores and the associated formation of new active sites have improved the HER rates of the MOFs by up to 500%. We envision that this strategy will allow the purposeful engineering of hierarchical MOFs and advance their applicability in environmental and energy technologies., While metal organic frameworks offer highly tunable materials for photocatalytic applications, catalytic site accessibility is a crucial parameter. Here, authors demonstrate selective ligand removal to introduce new active sites and mesopores and to enhance photocatalytic H2 evolution.

Since assembly processes are continuously increasing in complexity due to the growing number of product variants, the importance of digital assistance systems for handling complexity is growing to support human work in a suitable manner. However, the configuration of the assistance system for the increasing number of product variants can be particularly complex and time consuming. This paper therefore presents a concept to support the implementation of new product variants in existing digital assistance systems in a data-based approach by facilitating the process. Thus, an approach for possible support options depending on the individual data management of companies is identified and presented. The developed approach is examined on a conceptual level which is generally applicable. Finally, to identify the most suitable support within the presented approach, a benefit-oriented evaluation is derived as an outlook.

Die Diversifikation von Produkten erhöht die Komplexität in der Produktion, wodurch die Anforderungen an die Beschäftigten steigen. Durch den Einsatz digitaler Assistenzsysteme kann die menschliche Arbeit in der Produktion unterstützt werden. Dieser Beitrag beschäftigt sich mit den relevanten Funktionen eines digitalen Assistenzsystems als Diskussionsgrundlage bei deren Einführung. The diversification of products makes production more complex and jobs more demanding. Digital assistance systems can support human work in the production area. This article deals with the relevant functions of a digital assistance system as a basis for discussion when implementing them.

Worker churn is procyclical in the German labor market. We study the plant-level connection of churn and employment growth using the new Administrative Wage and Labor Market Flow Panel from 1975 to 2014. Churn is V-shaped in employment growth. Through analyzing this pattern by worker skill, age, and tenure, we establish that churn is unlikely to result from plant reorganization but rather from uncertainty about match quality. In a dynamic labor demand framework with a time-to-hire friction, churn can be interpreted as a manifestation of idiosyncratically stochastic separation shocks. These shocks become larger and more predictable during booms, leading to procyclical churn. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FTP/2007-2013) / ERC Grant agreement no. 282740. Felix Wellschmied gratefully acknowledges support from the Spanish Ministry of Economics through research grants ECO2014-56384-P, MDM 2014-0431, and Comunidad de Madrid MadEco-CM (S2015/HUM-3444). Heiko Stüber gratefully acknowledge support from the German Research Foundation (DFG) under priority program “The German Labor Market in a Globalized World” (SPP 1764). Christian Merkl gratefully acknowledge support from SPP 1764 and the Hans Frisch Stiftung.

An efficient compression technique based on hierarchical tensors for popular option pricing methods is presented. It is shown that the "curse of dimensionality" can be alleviated for the computation of Bermudan option prices with the Monte Carlo least-squares approach as well as the dual martingale method, both using high-dimensional tensorized polynomial expansions. This discretization allows for a simple and computationally cheap evaluation of conditional expectations. Complexity estimates are provided as well as a description of the optimization procedures in the tensor train format. Numerical experiments illustrate the favourable accuracy of the proposed methods. The dynamical programming method yields results comparable to recent Neural Network based methods., Comment: 26 pages, 3 figures, 5 tables, added affiliations and update acknowledgements

We consider rough stochastic volatility models where the variance process satisfies a stochastic Volterra equation with the fractional kernel, as in the rough Bergomi and the rough Heston model. In particular, the variance process is therefore not a Markov process or semimartingale, and has quite low H\"older-regularity. In practice, simulating such rough processes thus often results in high computational cost. To remedy this, we study approximations of stochastic Volterra equations using an $N$-dimensional diffusion process defined as solution to a system of ordinary stochastic differential equation. If the coefficients of the stochastic Volterra equation are Lipschitz continuous, we show that these approximations converge strongly with superpolynomial rate in $N$. Finally, we apply this approximation to compute the implied volatility smile of a European call option under the rough Bergomi and the rough Heston model.

ZusammenfassungDieser Beitrag beschreibt das Forschungsprojekt IntAKom (Intelligente Aufwertung der manuellen und teilautomatisierten Arbeit durch den Einsatz digitaler Kommunikationstechnologie) welches in Zusammenarbeit zwischen Forschung und Industrie konstruktive Ansätze guter digitaler Assistenz in der Produktion entwickelt und erprobt. Die Vorgehensweise wird an einem Anwendungsbeispiel aufgezeigt. Es wird beschrieben, wie das digitale Assistenzsystem in das Arbeitsumfeld integriert wurde. Gerade bei einer hohen Produktvielfalt erhöht sich die Komplexität in der Produktion. Die Beschäftigten können so durch den Einsatz digitaler Assistenzsysteme bei der Bewältigung der steigenden Anforderungen unterstützt werden. Darüber hinaus wird die Vorgehensweise zur Zielerreichung aus Sicht der Prozess-, Beschäftigten-, und Organisationsebene dargestellt und erste Projektergebnisse aufgezeigt. Auch die Erfolgsfaktoren für die Einführung eines digitalen Assistenzsystems werden abschließend in Form von Lessons learned formuliert.

Households face large income uncertainty that varies substantially over the business cycle. We examine the macroeconomic consequences of these variations in a model with incomplete markets, liquid and illiquid assets, and a nominal rigidity. Heightened uncertainty depresses aggregate demand as households respond by hoarding liquid “paper” assets for precautionary motives, thereby reducing both illiquid physical investment and consumption demand. We document the empirical response of portfolio liquidity and aggregate activity to surprise changes in idiosyncratic income uncertainty and find both to be quantitatively in line with our model. The welfare consequences of uncertainty shocks and of the policy response thereto depend crucially on a household's asset position

The diversification of products results in more challenging jobs for employees working within the production processes. Digital assistance is expected to increase the performance and flexibility of employees. This paper presents a framework to analyse the influence of digital assistance systems on essential target variables in a production system. For this purpose, functions of the digital assistance system, effects on the employee and key performance indicators are defined. From this, hypotheses are derived to describe the effect of digital assistance systems on employee performance. Subsequently, a concept for the verification of the framework and the hypotheses is presented. The approach allows to quantify the benefits of digital support in production. This supports acceptance and enables decision-makers to integrate digital technologies more benefit-oriented.

Introduction Transverse fractures of the olecranon are commonly fixed using tension-band wiring techniques. However the superficial nature of this area leads to high complication rates requiring removal of metalwork. The purpose of this retrospective study is to report and evaluate functional outcomes of polyethylene tension-band and bioabsorbable Magnesium alloy screw fixation of olecranon fractures. Methods A retrospective case-control study was undertaken. Demographics, injury type and post-operative details were collected. All patients were treated in the same institution by a single surgeon. Primary outcomes included radiographic healing and post-operative range of motion. Secondary outcome was post-operative complications. Results A total of five cases were identified. Mean age was 52.4. The control group was made up of six patients treated with a traditional tension band wire fixation. One patient in study group was lost to follow up. 80% of fractures in study group demonstrated anatomic post-operative radiographic union, compared with 83% of control group. All patients had range of motion above 100°, with full protonation and supination. One patient did have an extension lag of 15°. Conclusion Surgical repair of olecranon fractures is often complicated by the need for re-operation. This method provides both intramedullary fixation and conversion of distraction forces to compression forces with bioabsorbable materials, and aims to reduce the high re-operation rates commonly seen by avoiding the use of permanent indwelling metal hardware.