COVID-19 continues to have a major impact on US health and society. Robust research on the epidemiology of acute and post-acute COVID-19 remains fundamentally important to informing policy makers, scientists, as well as the public. This dissertation reports on the development of a large, diverse, United States general population-based meta-cohort with standardized, prospective ascertainment of SARS-CoV-2 and COVID-19, integrated with comprehensive pre-pandemic phenotyping from 14 extant cohort studies. Meta-cohort data were used to investigate risk and resilience factors for incident severe (hospitalized or fatal) and non-severe COVID-19 and correlates of time-to-recovery from SARS-CoV-2 infection. Results support the major acute and post-acute public health impact of COVID-19 and the vital role of modifiable (e.g., obesity, diabetes, cardiovascular disease) and non-modifiable (e.g., age, sex) risk factors for adverse COVID-19 outcomes. Findings suggest that standard primary care interventions—including obesity and cardiometabolic disease prevention and treatment, depression care, and vaccination—remain fundamental to COVID-19 risk mitigation among US adults. Given its longitudinal design and comprehensive pre-pandemic and pandemic-era measurements, the meta-cohort is well suited to support ongoing work regarding the public health impact of SARS-CoV-2 infection, COVID-19, post-acute sequelae, and pandemic-related social and behavioral changes across multiple health domains.

[pt] Diversos trabalhos publicados recentemente analisam o impacto da entrada de bancos estrangeiros no mercado bancário brasileiro. Muitos desses estudos avaliam o impacto dessa entrada no desempenho dos bancos nacionais, na oferta de crédito e em outras variáveis. Outros estudos enfatizam a oferta de crédito e o papel social dos bancos como fontes de financiamento para a iniciativa privada. Entretanto nenhum estudo amplo foi realizado com o objetivo de se identificar quais são os fatores determinantes da estratégia de alocação de ativos dos bancos com atividades de varejo no Brasil, e se esses fatores diferem entre bancos privados nacionais, bancos estrangeiros e bancos estatais. Para responder essas questões este estudo analisa dados das demonstrações financeiras de 35 bancos referentes ao período de 2000 a 2003. Os bancos da amostra foram selecionados na lista dos 50 Maiores Bancos por Ativos Totais (-) Intermediações, elaborada pelo Banco Central do Brasil, com um critério adicional de terem apresentado mais de cinco agências bancárias em qualquer ano do período analisado. Este trabalho enfatiza as características dos bancos como fatores determinantes da estratégia de alocação de ativos. Foram realizados testes estatísticos e regressões de dados em painel considerando três grupos de regressores: tamanho do banco, tipo de controle, e sua estrutura de financiamento. Os resultados sugerem que há diferenças no financiamento dos ativos entre bancos privados nacionais, estrangeiros e estatais. / [en] Several recent papers analyze the impact of foreign bank entry on the Brazilian bank market. Some of these studies assess the impact of those entrances on domestic banks` performance, on the overall credit supply, and on other variables. Other studies emphasize the credit supply and the banks` social role as financiers of the private sector. Nevertheless, no comprehensive study has aimed at identifying the determinant factors of asset allocation strategies of banks with retail activities in Brazil, and whether these factors vary according to different bank ownership control - private domestic, government, and foreign. With the objective of shedding some light on this subject, this work analyzes the financial statements of 35 banks in the time period 2000 - 2003. The sampled banks were selected from the list of the Largest 50 Banks by Total Assets (-) Intermediations, organized by The Central Bank of Brazil, with the additional criteria of having more than 5 offices in any year of the considered time period. The present work emphasizes the banks` characteristics as determinant factors of asset allocation strategies. Statistical tests and panel data analysis were run allowing for three regressor groups: bank size, ownership control, and funding structure. The results suggest there are significant differences between private domestic, government, and foreign banks in financing their assets.

An environmental mixture is composed of multiple environmental exposures. Quantifying this joint effect on health outcomes mirrors what occurs in nature, offering significant benefits to environmental epidemiological research. However, analyzing the impact of an environmental mixture poses numerous statistical and inferential challenges. Motivated by the Strong Heart Study (SHS), a prospective cohort study of cardiovascular disease (CVD) outcomes among three American Indian communities where urine samples were collected at three visits and analyzed for concentrations of various metal exposures, this dissertation aims to improve our ability to analyze the effect of multiple, continuous, and correlated exposures with complex relationships on a health outcome using observational study data, such as the metal mixture exposure in the SHS. The contributions of this dissertation address two challenges inherent in environmental mixture analyses: modeling methods and the transportability of estimated effects. In the first project presented in this dissertation, our goal was to evaluate the performance of available modeling methods for estimating the impact of an environmental mixture on survival outcomes. While survival time outcomes (also known as time-to-event outcomes) are very common in epidemiological studies, little attention has been given to examining the performance of existing modeling methods when estimating the effect of an environmental mixture on a survival outcome. In this chapter, we identified applicable and readily available modeling methods, assessed their performance through simulations replicating various real-world scenarios, and applied the selected methods to estimate the effect of a metal mixture on CVD incidence in the SHS. We examined proportional hazards (PH) based models as well as more flexible, machine learning-style models. Our simulations found that, when the PH assumption held, the effect estimates via flexible models had higher bias and variance compared to PH methods. However, when the PH assumption was violated, this discrepancy between the methods decreased and the more flexible methods achieved higher coverage. These simulation findings underscore the importance of demonstrating the robustness of findings across various modeling approaches in environmental epidemiology. In the SHS analysis, all methods found a significant, harmful effect of the metal mixture on incident CVD. However, the more flexible approaches found larger point estimates with wider confidence bands. The second and third projects of this dissertation focus on constructing a framework for transporting an environmental mixture effect across populations. Numerous methods exist for analyzing environmental mixture effects within a population where sample data is available for. However, being able to adjust these effects based on the exposure/covariate distribution of a different target population would enable more precise estimation of the mixture effect in that population. This, in turn, allows for more accurate estimation of effects for populations distinct from those sampled. This broadens available data sources and provides significant advantages to researchers and policymakers interested in specific populations. The second project leverages causal inference concepts to formally extend the transportability literature to the environmental mixtures context. We defined a relevant intervention with favorable properties concerning the exposure concentration positivity assumption and explicitly outline the assumptions needed to transport its effect across two observational studies. To assess whether the target population is well represented in the study population sample, which is required for the positivity of population membership assumption, a matching algorithm is proposed. Subject's environmental mixture exposure profiles are incorporated into subject matching on exposures and covariates between the two populations. Simulation results demonstrate that the matching algorithm effectively detects non-overlap across populations, with well-overlapped populations yielding minimally biased transported effect estimates, while those with insufficient overlap exhibit greater bias. Applying this framework, we estimated the effects of a metal mixture on coronary artery calcification (CAC) in the SHS cohort by transporting the effects observed in the Multi-Ethnic Study of Atherosclerosis (MESA). Although CAC was not directly measured in the SHS, its importance as a subclinical indicator of advanced atherosclerosis and its link to elevated cardiovascular risk underscore the significance of exploring its relationship with metal exposures in the SHS. Despite larger effects observed in the MESA population, significant effects persisted within the SHS, providing insights for innovative strategies in preventing and treating atherosclerosis progression among American Indian populations. In the third project, we turned our focus to violations of internal and external validity exchangeability assumptions. We proposed the use of a negative control exposure analysis modeled with Bayesian Kernel Machine Regression with hierarchical variable selection to identify unmeasured confounding in the context of multiple, continuous, and correlated exposures when exposures are measured at various time points. Additionally, we developed a novel method for detecting violations of transportability assumptions by assessing the transportability of an effect within a study population. If the internal validity assumptions are plausible, then the inability to transport an effect within a study population suggests the presence of unmeasured effect modification in the study sample. Through simulations, we demonstrated the efficacy of these methods in detecting unmeasured confounding and effect modification. We applied these methods to assess the robustness of the estimated effect of a metal mixture on fasting blood glucose levels in the SHS to violations of transportability assumptions and found evidence of both unmeasured confounding and effect modification. However, the internal effect estimate remained significant and robust to unmeasured confounding.

This dissertation examines the causal relationship between inward foreign direct investment (FDI) and economic growth (GDP) in SADC countries. The study investigates, within a panel data context, whether causation is short-term, long-term or both; and explores whether the causal relationship between the two variables differs according to income level. The study covered a panel of 15 SADC countries over the period 1980-2012. In order to assess whether the causal relationship between FDI inflows and economic growth is dependent on the level of income, the study divided the SADC countries into two groups, namely, the low-income and the middleincome countries. The study used the recently developed panel data analysis methods to examine this causal relationship. It adopted a three stage approach, which consists of panel unit root, panel cointegration and Granger causality to examine the dynamic causal relationship between the two variables. Panel unit root results show that both variables in the two SADC country groups were integrated of order one. Panel cointegration tests showed that the variables for low-income country group were not cointegrated, while the variables for the middle-income countries were cointegrated. Since the low-income country group panels were not cointegrated, Grangercausality tests were conducted within a VAR framework, while causality tests for the middleincome country group were conducted within an ECM framework. Panel Granger causality results for the low-income countries showed no evidence of causality in either direction. However, for the middle-income countries’ panel, there was evidence of a unidirectional causal flow from GDP to FDI in both the long- and short- run. The study concludes that the FDI-led growth hypothesis does not apply to SADC countries. The results imply that the recent high economic growth rates recorded in the SADC region, especially middle-income countries, have been attracting FDI. In other words, it is economic growth that drives FDI inflows into the SADC region, and not vice versa. These findings have profound policy implications for the SADC region at large and individual countries. / Economics / MCOM (Economics)

This dissertation examines the causal relationship between inward foreign direct investment (FDI) and economic growth (GDP) in SADC countries. The study investigates, within a panel data context, whether causation is short-term, long-term or both; and explores whether the causal relationship between the two variables differs according to income level. The study covered a panel of 15 SADC countries over the period 1980-2012. In order to assess whether the causal relationship between FDI inflows and economic growth is dependent on the level of income, the study divided the SADC countries into two groups, namely, the low-income and the middleincome countries. The study used the recently developed panel data analysis methods to examine this causal relationship. It adopted a three stage approach, which consists of panel unit root, panel cointegration and Granger causality to examine the dynamic causal relationship between the two variables. Panel unit root results show that both variables in the two SADC country groups were integrated of order one. Panel cointegration tests showed that the variables for low-income country group were not cointegrated, while the variables for the middle-income countries were cointegrated. Since the low-income country group panels were not cointegrated, Grangercausality tests were conducted within a VAR framework, while causality tests for the middleincome country group were conducted within an ECM framework. Panel Granger causality results for the low-income countries showed no evidence of causality in either direction. However, for the middle-income countries’ panel, there was evidence of a unidirectional causal flow from GDP to FDI in both the long- and short- run. The study concludes that the FDI-led growth hypothesis does not apply to SADC countries. The results imply that the recent high economic growth rates recorded in the SADC region, especially middle-income countries, have been attracting FDI. In other words, it is economic growth that drives FDI inflows into the SADC region, and not vice versa. These findings have profound policy implications for the SADC region at large and individual countries. / Economics / M. Com. (Economics)

[pt] Considerando a importância da estrutura de capital para as finanças empresariais, e apesar de não ainda existir consenso sobre a existência de uma estrutura ótima de capital, buscamos neste trabalho investigar à luz da Teoria da Hierarquização das Fontes de Financiamento, desenvolvida por Myers (1984), como a estrutura de capital das empresas brasileiras de capital aberto, no período de 1998 a 2002, estaria associada a uma dada hierarquia de preferência por fontes de financiamento, dentro da lógica proposta pelo autor, onde as empresas utilizariam primeiramente o autofinanciamento, em seguida recorreriam ao uso de dívidas, e como última opção optariam por emitir ações. Desta forma, este trabalho não visa discutir a problemática da existência ou não de uma estrutura ótima de capitais, mas sim analisar empiricamente a importância e validade dos diversos fatores apontados na literatura como determinantes da Estrutura de Capital das Empresas: Dimensão ou Tamanho, Oportunidades de Crescimento, Composição do Ativo, Lucratividade, Risco, propondo e verificando, inclusive, a significância de novas variáveis independentes como o Controle Acionário, Impacto Cambial, da Inflação e da Taxa de Juros. / [en] In view of the importance of the capital structure to corporate finance, and inspite of not existing consensus about the existence of the optimal capital structure yet, we seek in this work to research how the Capital Structure of Open Capital Brazilian Companies, from 1998 untill 2002, would be associated to a specific Pecking Order, inside the logical proposed by Myers (1984). In this way, this work does not try to discuss the existence or not of one optimal capital structure, but analyses empirically the importance and the validity of the many factors pointed in the literature as determinants of the Companies Capital Structure: Dimension, Growth Oportunity, Asset Composition, Profitability, Risk, also proposing and verifying the significance of new independent variables like the type of capital control, the impact of currency devaluation, inflation and the interest levels.

Organizzata in tre saggi, questa tesi si pone l’obiettivo di consentire una migliore comprensione del legame tra crescita e istituzioni, e dei meccanismi attraverso cui gli assetti istituzionali possono condizionare i sentieri economici. Riconoscendo, sulla base di considerazioni storiche, il potere esemplificativo delle ex Repubbliche Socialiste Sovietiche e della loro comune esperienza passata, questo lavoro fornisce, da un lato, una struttura empirica di riferimento per esaminare l’impatto sulla performance economica di un insieme di istituzioni, concretamente legate al funzionamento dell’attività economica; dall’altro, approfondisce lo studio degli effetti e delle determinanti delle azioni di policy. Il primo saggio offre una disamina della letteratura riguardante il legame crescita e istituzioni, fornendo un quadro esaustivo degli sviluppi teorici ed empirici, e illustra diversi aspetti che possono essere concepiti come obiettivi per la ricerca futura; il secondo, attraverso la costruzione di un modello statico e di un modello dinamico, quantifica l’impatto delle istituzioni economiche sui sentieri di crescita di questi paesi, impiegando e analizzando numerose tecniche di stima; il terzo saggio formula diverse specificazioni e affronta il tema rilevante del ruolo degli interventi di policy sullo sviluppo economico e dell’effetto delle istituzioni politiche su comportamenti e decisioni del governo. / Organized in three essays, this thesis aims at achieving a better understanding of the link between growth and institutions, and of the mechanisms through which the institutional arrangements affect the economic paths. Exploiting the past common experience of the Former Soviet Union economies, this work provides an empirical framework to examine the impact on the economic performance of a set of institutions concretely related to the “functioning” of the economic activity and offers a first attempt to include in this research program the study of the consequences of the government actions. The first essay offers a thorough review of the literature researching on the link between economic growth and institutions, and elucidates several issues that deserve further attention; the second develops a static and a dynamic approach to assess, using multiple estimation techniques, the impact of a set of economic institutions on the growth paths of these countries; the third essay, through several formal specifications, deals with the relevant issue of the role of policy measures and of the effect of the political institutions on the governments behaviour.

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