Unit-Root tests in high-dimensional panels

The four chapters of this PhD thesis all concern panel unit-root tests, i.e., tests for the stationarity properties of a large number of time-series. The first chapter analyzes the testing problem in case stationary alternatives offset explosives ones. While the panel units are assumed to be independent in the first chapter, the subsequent chapters consider ‘second-generation’ panel unit-root tests which allow the different time series to be correlated through a factor structure. Chapter 2 considers two common approaches of modeling this dependence and shows that the associated unit-root testing problems are asymptotically equivalent. Using Le Cam’s theory of statistical experiments, an optimal test is derived jointly in both setups. Chapter 3 studies unit-root tests for the underlying common factors rather than the idiosyncratic parts. It is demonstrated that unit root tests can be applied to a number of different factor estimates as if the factor was observed. A similar result is obtained for the case in which the factors have non-zero mean innovations. The final Chapter 4 revisits the testing problem for the unobserved common factors but exploits additional observed covariates that are known to be stationary to obtain higher powers

Local Asymptotic Equivalence of the Bai and Ng (2004) and Moon and Perron (2004) Frameworks for Panel Unit Root Testing

This paper considers unit-root tests in large n and large T heterogeneous panels with cross-sectional dependence generated by unobserved factors. We reconsider the two prevalent approaches in the literature, that of Moon and Perron (2004) and the PANIC setup proposed in Bai and Ng (2004). While these have been considered as completely different setups, we show that, in case of Gaussian innovations, the frameworks are asymptotically equivalent in the sense that both experiments are locally asymptotically normal (LAN) with the same central sequence. Using Le Cam's theory of statistical experiments we determine the local asymptotic power envelope and derive an optimal test jointly in both setups. We show that the popular Moon and Perron (2004) and Bai and Ng (2010) tests only attain the power envelope in case there is no heterogeneity in the long-run variance of the idiosyncratic components. The new test is asymptotically uniformly most powerful irrespective of possible heterogeneity. Moreover, it turns out that for any test, satisfying a mild regularity condition, the size and local asymptotic power are the same under both data generating processes. Thus, applied researchers do not need to decide on one of the two frameworks to conduct unit root tests. Monte-Carlo simulations corroborate our asymptotic results and document significant gains in finite-sample power if the variances of the idiosyncratic shocks differ substantially among the cross sectional units

Dietary habits, traveling and the living situation potentially influence the susceptibility to SARS-CoV-2 infection: results from healthcare workers participating in the RisCoin Study.

PURPOSE To explore occupational and non-occupational risk and protective factors for the coronavirus disease 2019 (COVID-19) in healthcare workers (HCWs). METHODS Serum specimens and questionnaire data were obtained between October 7 and December 16, 2021 from COVID-19-vaccinated HCWs at a quaternary care hospital in Munich, Germany, and were analyzed in the RisCoin Study. RESULTS Of 3,696 participants evaluated, 6.6% have had COVID-19 at least once. Multivariate logistic regression analysis identified working in patient care occupations (7.3% had COVID-19, 95% CI 6.4-8.3, Pr = 0.0002), especially as nurses, to be a potential occupation-related COVID-19 risk factor. Non-occupational factors significantly associated with high rates of the disease were contacts to COVID-19 cases in the community (12.8% had COVID-19, 95% CI 10.3-15.8, Pr < 0.0001), being obese (9.9% had COVID-19, 95% CI 7.1-13.5, Pr = 0.0014), and frequent traveling abroad (9.4% had COVID-19, 95% CI 7.1-12.3, Pr = 0.0088). On the contrary, receiving the basic COVID-19 immunization early during the pandemic (5.9% had COVID-19, 95% CI 5.1-6.8, Pr < 0.0001), regular smoking (3.6% had COVID-19, 95% CI 2.1-6.0, Pr = 0.0088), living with the elderly (3.0% had COVID-19, 95% CI 1.0-8.0, Pr = 0.0475), and frequent consumption of ready-to-eat meals (2.6% had COVID-19, 95% CI 1.1-5.4, Pr = 0.0045) were non-occupational factors potentially protecting study participants against COVID-19. CONCLUSION The newly discovered associations between the living situation, traveling as well as dietary habits and altered COVID-19 risk can potentially help refine containment measures and, furthermore, contribute to new mechanistic insights that may aid the protection of risk groups and vulnerable individuals

The multimodal Munich Clinical Deep Phenotyping study to bridge the translational gap in severe mental illness treatment research

Introduction: Treatment of severe mental illness (SMI) symptoms, especially negative symptoms and cognitive dysfunction in schizophrenia, remains a major unmet need. There is good evidence that SMIs have a strong genetic background and are characterized by multiple biological alterations, including disturbed brain circuits and connectivity, dysregulated neuronal excitation-inhibition, disturbed dopaminergic and glutamatergic pathways, and partially dysregulated inflammatory processes. The ways in which the dysregulated signaling pathways are interconnected remains largely unknown, in part because well-characterized clinical studies on comprehensive biomaterial are lacking. Furthermore, the development of drugs to treat SMIs such as schizophrenia is limited by the use of operationalized symptom-based clusters for diagnosis. Methods: In line with the Research Domain Criteria initiative, the Clinical Deep Phenotyping (CDP) study is using a multimodal approach to reveal the neurobiological underpinnings of clinically relevant schizophrenia subgroups by performing broad transdiagnostic clinical characterization with standardized neurocognitive assessments, multimodal neuroimaging, electrophysiological assessments, retinal investigations, and omics-based analyzes of blood and cerebrospinal fluid. Moreover, to bridge the translational gap in biological psychiatry the study includes in vitro investigations on human-induced pluripotent stem cells, which are available from a subset of participants. Results: Here, we report on the feasibility of this multimodal approach, which has been successfully initiated in the first participants in the CDP cohort; to date, the cohort comprises over 194 individuals with SMI and 187 age and gender matched healthy controls. In addition, we describe the applied research modalities and study objectives. Discussion: The identification of cross-diagnostic and diagnosis-specific biotype-informed subgroups of patients and the translational dissection of those subgroups may help to pave the way toward precision medicine with artificial intelligence-supported tailored interventions and treatment. This aim is particularly important in psychiatry, a field where innovation is urgently needed because specific symptom domains, such as negative symptoms and cognitive dysfunction, and treatment-resistant symptoms in general are still difficult to treat

Job Loss Fears and (Extreme) Party Identification: First Evidence from Panel Data

There is a large body of literature analyzing the relationship between objective economic conditions and voting behavior, but there is very little evidence of how perceived economic insecurity impacts on political preferences. Using seventeen years of household panel data from the German Socio-Economic Panel, we examine whether job loss fears impact on individuals' party identification. Consistent with rational choice theory, we find strong and robust evidence that job loss fears foster affinity for parties at the far right-wing of the political spectrum. However, our empirical estimates do not suggest that job loss fears result in people withdrawing their support from political parties altogether

Unit-Root tests in high-dimensional panels

The four chapters of this PhD thesis all concern panel unit-root tests, i.e., tests for the stationarity properties of a large number of time-series. The first chapter analyzes the testing problem in case stationary alternatives offset explosives ones. While the panel units are assumed to be independent in the first chapter, the subsequent chapters consider ‘second-generation’ panel unit-root tests which allow the different time series to be correlated through a factor structure. Chapter 2 considers two common approaches of modeling this dependence and shows that the associated unit-root testing problems are asymptotically equivalent. Using Le Cam’s theory of statistical experiments, an optimal test is derived jointly in both setups. Chapter 3 studies unit-root tests for the underlying common factors rather than the idiosyncratic parts. It is demonstrated that unit root tests can be applied to a number of different factor estimates as if the factor was observed. A similar result is obtained for the case in which the factors have non-zero mean innovations. The final Chapter 4 revisits the testing problem for the unobserved common factors but exploits additional observed covariates that are known to be stationary to obtain higher powers

Politik(er) im Fernsehen. Zum Wandel der Politikvermittlung in einer sich verändernden Medienlandschaft.

Demokratische Systeme zeichnen sich vor allem dadurch aus, daß in ihnen politische Machtdurch Wahlen und nur auf Zeit vergeben wird. Politische Herrschaft ist also zustimmungs-abhängig.Aus diesem Grund kann die öffentliche Darstellung von Politik, die die Voraus-setzungund Grundlage für freie Meinungsbildung und Entscheidungsfindung des Wählersbildet, nicht als lästige Pflicht angesehen werden, sondern sie ist vielmehr die Basis für Herr-schaftin einer modernen Demokratie.2Die Darstellung und Vermittlung der Politik ist einwesentlicher Bestandteil des Wettbewerbs um Stimmen und Zustimmung. Der Politikerverhält sich dementsprechend wie ein Oligopolist auf dem politischen Markt.3Nur imallereinfachsten, abstraktesten Modell sind die Wähler vollständig informiert und in derLage, die künftigen Leistungen zu vergleichen, die sie von den konkurrierenden Parteienerwarten. Aber auch dann schon stellt diese auf den ersten Blick leichte Urteilsfindung hoheAnsprüche an den Wähler. Um eine im Downschen Sinne rationale Wahl zu treffen, muß ereine Vielzahl von Informationen sammeln, werten und verarbeiten. Dem Charakter reprä-sentativerDemokratien westlichen Typus entspricht es nun, daß nur sehr wenige direkteVerbindungslinien zwischen allgemeiner Öffentlichkeit und Regierungstätigkeit bestehen.Zwischen Staat und Gesellschaft ist vielmehr ein sogenanntes intermediäres Systemgeschaltet, das vielfältige Vermittlungsaufgaben in beiden Richtungen übernommen hat.Organisatorische Bestandteile des intermediären Bereichs sind vor allem Bildungssysteme,politische Parteien, Vereine, Interessenverbände, soziale Bewegungen und nicht zuletzt diepublizistischen Massenmedien