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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

台灣失業率與犯罪關係之初探—不同模型之比較 / Exploration of the relationship between unemployment rate and crimes in Taiwan:A Comparison between Models

魏大耕 Unknown Date (has links)
在過去研究犯罪經濟學的理論文獻上,失業率對各犯罪類型的影響為正向關係,但在實証文獻上的研究發現,卻有愈來愈多的証據支持此二個變數間的負向或無關係。為了解釋上述正向與負向間相反的矛盾關係,本篇論文嘗試利用兩種模型(非參數與非參數模型)與兩種效果(機會效果與動機效果)來解釋此二變數間的關係,此亦是本論文主要貢獻。其中機會效果是用以解釋失業率與犯罪間的負向關係,動機效果則用以解釋正向關係。在非參數模型中,利用失業率為景氣循環的代理變數,發現失業率與竊盜間存在正向關係,此與大多實証研究相符;失業率則和妨害風化與殺人犯罪間呈現負向相關;失業率與傷害罪間則沒有明顯正負關係。研究亦顯示,不同的犯罪類型在不同的參數模型下,統計的顯著性亦有不同,而在不同年齡層(青少年與成年人)的犯罪模型則更與理論模型結論相符。 / According to the theoretical literature on criminal economics, unemployment rate tends to be positively correlated to all types of crimes. However, more and more empirical evidence suggests otherwise. In order to clarify the relationship, this study exploits both nonparametric and parametric models and considers two effects, including opportunity and motivation effects. The presence of the opportunity effect leads to be a negative correlation between unemployment rate and crimes, while the presence of the motivation effect gives a positive correlation. Under nonparametric model where unemployment rate is used as a proxy for business cycles, we only found that there is positive correlation between unemployment rate and robbery, while obscenity and homicide are found to be negatively correlated with unemployment rate. This is in line with most empirical studies. Little correlation evidence is found for unemployment and other types of crimes. Under parametric model, the study indicates that the statistical significance differs in models, and depends on crime variable used. We found more consistent results with theoretic models for the age groups (teenagers and adults).
242

Essais sur les frictions financières dans les modèles d'équilibre général dynamique

Solomon, Bernard Daniel 06 1900 (has links)
Cette thèse examine les effets des imperfections des marchés financiers sur la macroéconomie. Plus particulièrement, elle se penche sur les conséquences de la faillite dans les contrats financiers dans une perspective d'équilibre général dynamique. Le premier papier construit un modèle qui utilise l'avantage comparatif des banques dans la gestion des situations de détresse financière pour expliquer le choix des firmes entre les prêts bancaires et les prêts du marché financier. Le modèle réussit à expliquer pourquoi les firmes plus petites préfèrent le financement bancaire et pourquoi les prêts bancaires sont plus répandus en Europe. Le premier fait est expliqué par le lien négatif entre la valeur nette de l'entreprise et la probabilité de faire faillite. Le deuxième fait s'explique par le coût fixe d'émission de bons plus élevé en Europe. Le deuxième papier examine l'interaction entre les contraintes de financement affectant les ménages et les firmes. Une interaction positive pourrait amplifier et augmenter la persistance de l'effet d'un choc agrégé sur l'économie. Je construis un nouveau modèle qui contient des primes de financement externes pour les firmes et les ménages. Dans le modèle de base avec prix et salaires flexibles, j'obtiens une faible interaction négative entre les coûts de financement des firmes et des ménages. Le facteur clé qui explique ce résultat est l'effet du changement contre cyclique du coût de financement des ménages sur leur offre de travail et leur demande de prêts. Dans une période d'expansion, cet effet augmente les taux d'intérêt, réduit l'investissement et augmente le coût de financement des entreprises. Le troisième papier ajoute les contraintes de financement des banques dans un modèle macroéconomiques avec des prêts hypothécaires et des fluctuations dans les prix de l'immobilier. Les banques dans le modèle ne peuvent pas complètement diversifier leurs prêts, ce qui génère un lien entre les risques de faillite des ménages et des banques. Il y a deux effets contraires des cycles économiques qui affectent la prime de financement externe de la banque. Premièrement, il y a un lien positif entre le risque de faillite des banques et des emprunteurs qui contribue à rendre le coût de financement externe des banques contre cyclique. Deuxiément, le lissage de la consommation par les ménages rend la proportion de financement externe des banques pro cyclique, ce qui tend à rendre le coût de financement bancaire pro cyclique. En combinant ces deux effets, le modèle peut reproduire des profits bancaires et des ratios d'endettement bancaires pro cycliques comme dans les données, mais pour des chocs non-financiers les frictions de financement bancaire dans le modèle n'ont pas un effet quantitativement significatif sur les principales variables agrégées comme la consommation ou l'investissement. / This Dissertation examines the effect of financial market imperfections on the Macroeconomy. More particularly, it focuses on the consequences of equilibrium default using a Dynamic General Equilibrium approach. The first paper builds a dynamic general equilibrium model that emphasizes banks' comparative advantage in monitoring financial distress in order to explain firms' choice between bank loans and market debt. Banks can deal with financial distress more cheaply than bond holders, but this requires a higher initial expenditure proportional to the loan size. In contrast, bond issues may involve a small fixed cost. Entrepreneurs' choice of bank or bond financing depends on their net worth. The model can explain why smaller firms tend to use more bank financing and why bank financing is more prevalent in Europe than in the US. The first fact can be explained by the negative link between the net worth of a business and its default probability. Explaining the second fact requires taking into account the higehr fixed cost of issuing market debt in Europe. The second paper examines the possibility of feedback effects between between the financing constraints of households and of firms. A positive interaction between the financial strength of household and firm balance sheets may amplify aggregate shocks and increase the persistence of aggregate fluctuations. I develop a new model that incorporates both firm and household external finance spreads and time varying leverage. Contrary to a common intuition, the baseline Real Business Cycle model with credit constraints produces a small negative interaction between the costs of external financing for firms and households. The key factor in this result is the effect of changes in the external finance premium on borrowers' labour supply and the demand for loans. The reduction in households' cost of borrowing in a boom decreases labour supply and raises houshold loan demand. This increases interest rates, crowds out investment, and raises borrowing costs for financially constrained firms. The third paper integrates household financing frictions with bank financing frictions and house price fluctuations in a dynamic general equilibrium model. The key assumption in the model is that a bank cannot fully diversify shocks, leading to a link between household and bank sectors' default risks. The cyclical behaviour of banks' external funding cost is determined by two main factors. On one hand, booms improve the financial health of the banks' borrowers which tends to reduce the cost of bank funding. On the other hand, consumption smoothing by savers and borrowers during booms increases the proportion of external financing in the banks' balance sheet which tends to increase the cost of bank funding. As a result of these opposing effects, the model matches procyclical profits and leverage in the financial sector, as observed in the data, but for non financial shocks the banking frictions in the model have an insignificant impact on the main macroeconomic aggregates such as output, consumption and investment.
243

Peněžní expanze a ekonomické krize: Rakouský pohled / Monetary Expansion and Economic Crises: An Austrian Perspective

Jára, Karel January 2014 (has links)
The study of economic crises has been a major topic of interest in economics since at least the Great Depression and it has come to the fore once again after the latest crisis of late 2000s. It has also been one of the key themes for the Austrian school of economics in the form of the Austrian Business Cycle Theory (ABCT), which puts emphasis on monetary factors influencing capital structure of the economy. In this thesis we provide a comprehensive exposition of the distinctive points of Austrian approach to the study of markets, the ABCT's propositions and conclusions and also the most important criticism of the theory and replies to it. The theoretical part is accompanied by an empirical illustration on the economy of the United States of America in the period starting at the end of the latest crisis. Powered by TCPDF (www.tcpdf.org)
244

Trois essais sur les liens entre les marchés immobiliers et l’économie / Three essays on the linkages between real estate markets and the wider economy

Bouchouicha, Ranoua 13 June 2013 (has links)
Cette thèse présente trois essais qui fournissent un aperçu global de la manière dont les chocs au niveau du marché immobilier affectent l'économie et vice versa.Dans le premier essai, nous utilisons des modèles de Markov à changement de régimes avec des probabilités qui dépendent du temps et des probabilités fixes afin d'évaluer l'ampleur des mécanismes de transmission entre le marché de placements immobiliers, le marché du logement et le marché boursier au Royaume-Uni et aux États-Unis. Nous montrons que la relation entre les marchés immobiliers et les marchés des actions est plus significative quand les marchés immobiliers sont considérés comme des variables explicatives.Dans le deuxième essai, nous introduisons le marché d'immobilier commercial afin d'identifier les interactions entre différents marchés immobiliers et certaines variables macroéconomiques. Nous utilisons une fonction de cohérence dynamique dans un cadre d'analyse spectrale pour évaluer ces liens. Les résultats montrent une tendance commune à long terme des différents marchés immobiliers. Aux États-Unis, les canaux de transmissions: richesse et dépenses de logement sont très conducteurs en cas de crise immobilière. Cependant, au Royaume-Uni, seulement le canal de la richesse s'avère conducteur dans les périodes de ralentissement du marché immobilier. Le troisième essai développe un cadre pour modéliser le marché de logement français. Nous élaborons et estimons un modèle de recherche d'équilibre du marché du logement segmenté entre locataires et propriétaires se caractérisant par une hétérogénéité des besoins de logement. Notre modèle reproduit l'évolution des prix de l'immobilier sur le marché français de 1996 à 2006, ainsi que la corrélation entre le prix, l'âge et la durée. En outre, nous montrons que l'inadéquation des individus avec leur logement est fortement corrélée avec le cycle de vie, et que l'agrégation de ces événements peut empêcher l'équilibre du marché à long terme. / This thesis contains three essays on the linkages between real estate and the wider economy. We provide a global snapshot of how shocks in the real estate market affect the economy and vice versa. In the first essay, we use Markov Switching models with time varying transition probabilities and fixed time transition probabilities in order to assess the magnitude of the transmission mechanisms between real estate markets and stock markets in the UK and the US. The results show a more significant credit price effect than a wealth effect. In addition, the different features of the linkages between real estate markets and stock markets are explained by the difference in the indices constructions of the housing prices and the REIT models in the two countries.In the second essay, an additional property market is included to further investigate the links of different real estate markets with some key macroeconomic variables. We use a dynamic coherence function in a spectral framework to assess these linkages. We find a common trend that drives all the real estate markets, particularly in the long run. The results show that in the US, wealth and housing expenditure channels are very conductive during real estate crises. However, for the UK, only the wealth is significant as a transmission channel during real estate market downturns. The third essay develops a framework that models the French housing market. We specify and estimate an equilibrium search model of the housing market that features a segmented housing market with heterogeneity in housing need. Our model reproduces almost exactly the evolution of French housing prices from 1996 to 2006, along with the correlation between price, age and duration. In addition we show that individuals mismatch is highly correlated with the life-cycle, and that aggregation of such events can prevent the market from clearing over a long period of time.
245

Hétérogénéités régionales et politiques macroéconomiques dans une zone monétaire le cas de l'UEMOA / Regional heterogeneities and macroeconomic policies in a monetary area the case of the WAEMU

Diallo, Hamidou 18 December 2018 (has links)
Cette thèse tire les enseignements de la zone Euro qui représente la phase la plus avancée de l’intégration économique au sein de l’Union Européenne. Cependant, force est de constater que la zone euro affiche des lacunes en termes de mécanismes d’ajustement alternatifs. Ainsi malgré les avancées considérables, cette intégration économique et institutionnelle semble insuffisante pour absorber les chocs asymétriques sur les États. Nous avons utilisé diverses approches (baromètres de convergence, classification par arbre de décision et modèle de Merton) pour évaluer l’efficacité des politiques économiques au sein de l’UEMOA. Nous avons étudié, à partir de données empiriques allant de 1994 à 2015, l’hétérogénéité des principaux agrégats macroéconomiques entre les pays de la zone et leurs évolutions dans le temps. Contrairement aux attentes, des différences existent encore entre les pays. Selon l’objectif de politique macroéconomique mesuré (croissance économique, inflation, chômage), nos résultats révèlent que les changements dans les performances des groupes constitués sont expliqués soit par des migrations entre les groupes, soit par les changements à l’intérieur des groupes. Finalement, nos investigations montrent que l’élargissement à la CEDEAO amplifie ces divergences. Nos résultats montrent enfin une bonne performance de la règle de Taylor comparativement à l’inflation cible depuis 2003. Cette règle serait une "conduite de base" adaptable à la politique de la future banque centrale après avoir levé la difficulté à déterminer les valeurs de référence de l’équation dans ces espaces économiques hétérogènes. / This paper draws lessons from the Eurozone which represents the most advanced stage of economic integration in the European Union. However the alternative adjustment mechanisms in place there prove to be insufficient to absorb asymmetric shocks endured by member states. We used various methods such as convergence barometers, decision tree classification, and Merton model in order to assess the effectiveness of the economic policies in place within the WAEMU . We studied, through empirical data from 1994 to 2015, the heterogeneity of the main macroeconomic aggregates between the countries of the area and it’s evolution over time. Contrary to expectations, discrepancies still exist between countries. In accordance with the goal of macroeconomic policy measured, our results reveal that either the effects of migration between groups, or the changes in performance within groups give an account of the changes in performance inside groups. Our investigations eventually brings to light that the expansion to the ECOWAS amplifies the divergences.Lastly, our results show that the Taylor rule has been well put to use in comparison to targeted inflation since 2003. This rule can be regarded as a "basic rule" adaptable to the policy of the future central bank after having lifted the difficulty in determining the reference values in these heterogeneous economic areas.
246

Essays on business cycle analysis and demography

Sarferaz, Samad 28 June 2010 (has links)
Diese Arbeit besteht aus vier Essays, die empirische und methodische Beiträge zur Messung von Konjunkturzyklen und deren Zusammenhänge zu demographischen Variablen liefern. Der erste Essay analysiert unter Zuhilfenahme eines Bayesianischen Dynamischen Faktormodelles die Volatilität des US-amerikanischen Konjunkturzyklus seit 1867. In dem Essay wird gezeigt, dass die Volatilität in der Periode vor dem Ersten Weltkrieg und nachdem Zweiten Weltkrieg niedriger war als in der Zwischenkriegszeit. Eine geringere Volatilität für die Periode nach dem Zweiten Weltkrieg im Vergleich zu der Periode vor dem Ersten Weltkrieg kann nicht bestätigt werden. Der zweite Essay hebt die Bayesianischen Eigenschaften bezüglich dynamischer Faktormodelle hervor. Der Essay zeigt, dass die ganze Analyse hindurch - im Gegensatz zu klassischen Ansätzen - keine Annahmen an die Persistenz der Zeitreihen getroffen werden muss. Des Weiteren wird veranschaulicht, wie im Bayesianischen Rahmen die Anzahl der Faktoren bestimmt werden kann. Der dritte Essay entwickelt einen neuen Ansatz, um altersspezifische Sterblichkeitsraten zu modellieren. Kovariate werden mit einbezogen und ihre Dynamik wird gemeinsam mit der von latenten Variablen, die allen Alterklassen zugrunde liegen, modelliert. Die Resultate bestätigen, dass makroökonomische Variablen Prognosekraft für die Sterblichkeit beinhalten. Im vierten Essay werden makroökonomischen Zeitreihen zusammen mit altersspezifischen Sterblichkeitsraten einer strukturellen Analyse unterzogen. Es wird gezeigt, dass sich die Sterblichkeit von jungen Erwachsenen in Abhängigkeit von Konjunkturzyklen deutlich von den der anderen Alterklassen unterscheidet. Daher sollte in solchen Analysen, um Scheinkorrelation vorzubeugen, zwischen den einzelnen Altersklassen differenziert werden. / The thesis consists of four essays, which make empirical and methodological contributions to the fields of business cycle analysis and demography. The first essay presents insights on U.S. business cycle volatility since 1867 derived from a Bayesian dynamic factor model. The essay finds that volatility increased in the interwar periods, which is reversed after World War II. While evidence can be generated of postwar moderation relative to pre-1914, this evidence is not robust to structural change, implemented by time-varying factor loadings. The second essay scrutinizes Bayesian features in dynamic index models. The essay shows that large-scale datasets can be used in levels throughout the whole analysis, without any pre-assumption on the persistence. Furthermore, the essay shows how to determine the number of factors accurately by computing the Bayes factor. The third essay presents a new way to model age-specific mortality rates. Covariates are incorporated and their dynamics are jointly modeled with the latent variables underlying mortality of all age classes. In contrast to the literature, a similar development of adjacent age groups is assured, allowing for consistent forecasts. The essay demonstrates that time series of covariates contain predictive power for age-specific rates. Furthermore, it is observed that in particular parameter uncertainty is important for long-run forecasts, implicating that ignoring parameter uncertainty might yield misleadingly precise predictions. In the fourth essay the model developed in the third essay is utilized to conduct a structural analysis of macroeconomic fluctuations and age-specific mortality rates. The results reveal that the mortality of young adults, concerning business cycles, noticeably differ from the rest of the population. This implies that differentiating closely between particular age classes, might be important in order to avoid spurious results.
247

Essays on financial markets and the macroeconomy

Mönch, Emanuel 13 December 2006 (has links)
Diese Arbeit besteht aus vier Essays, die empirische und methodische Beiträge zu den Gebieten der Finanzmarktökonomik und der Makroökonomik liefern. Der erste Essay beschäftigt sich mit der Spezifikation der Investoren verfügbaren Informationsmenge in Tests bedingter Kapitalmarktmodelle. Im Speziellen schlägt es die Verwendung dynamischer Faktoren als Instrumente vor. Diese fassen per Konstruktion die Information in einer Vielzahl von Variablen zusammen und stellen daher intuitive Maße für die Investoren zur Verfügung stehenden Informationen dar. Es wird gezeigt, dass so die Schätzfehler bedingter Modelle im Vergleich zu traditionellen, auf einzelnen Indikatoren beruhenden Modellvarianten substantiell verringert werden. Ausgehend von Ergebnissen, dass die Zentralbank zur Festlegung des kurzfristigen Zinssatzes eine große Menge an Informationen berücksichtigt, wird im zweiten Essay im Rahmen eines affinen Zinsstrukturmodells eine ähnliche Idee verwandt. Speziell wird die Dynamik des kurzfristigen Zinses im Rahmen einer Faktor-Vektorautoregression modelliert. Aufbauend auf dieser dynamischen Charakterisierung der Geldpolitik wird dann die Zinsstruktur unter der Annahme fehlender Arbitragemöglichkeiten hergeleitet. Das resultierende Modell liefert bessere Vorhersagen US-amerikanischer Anleihenzinsen als eine Reihe von Vergleichsmodellen. Der dritte Essay analysiert die Vorhersagekraft der Zinsstrukturkomponenten "level", "slope", und "curvature" im Rahmen eines dynamischen Faktormodells für makroökonomische und Zinsdaten. Das Modell wird mit einem Metropolis-within-Gibbs Sampling Verfahren geschätzt, und Überraschungsänderungen der drei Komponenten werden mit Hilfe von Null- und Vorzeichenrestriktionen identifiziert. Die Analyse offenbart, dass der "curvature"-Faktor informativer in Bezug auf die zukünftige Entwicklung der Zinsstruktur und der gesamtwirtschaftlichen Aktivität ist als bislang vermutet. Der vierte Essay legt eine monatliche Chronologie der Konjunkturzyklen im Euro-Raum vor. Zunächst wird mit Hilfe einer verallgemeinerten Interpolationsmethode eine monatliche Zeitreihe des europäischen BIP konstruiert. Anschließend wird auf diese Zeitreihe ein Datierungsverfahren angewandt, das kurze und flache Konjunkturphasen ausschließt. / This thesis consists of four essays of independent interest which make empirical and methodological contributions to the fields of financial economics and macroeconomics. The first essay deals with the proper specification of investors’ information set in tests of conditional asset pricing models. In particular, it advances the use of dynamic factors as conditioning variables. By construction, dynamic factors summarize the information in a large number of variables and are therefore intuitively appealing proxies for the information set available to investors. The essay demonstrates that this approach substantially reduces the pricing errors implied by conditional models with respect to traditional approaches that use individual indicators as instruments. Following previous evidence that the central bank uses a large set of conditioning information when setting short-term interest rates, the second essay employs a similar insight in a model of the term structure of interest rates. Precisely, the dynamics of the short-term interest rate are modelled using a Factor-Augmented Vector-Autoregression. Based on this dynamic characterization of monetary policy, the term structure of interest rates is derived under the assumption of no-arbitrage. The resulting model is shown to provide superior out-of-sample forecasts of US government bond yields with respect to a number of benchmark models. The third essay analyzes the predictive information carried by the yield curve components level, slope, and curvature within a joint dynamic factor model of macroeconomic and interest rate data. The model is estimated using a Metropolis-within-Gibbs sampling approach and unexpected changes of the yield curve components are identified employing a combination of zero and sign restrictions. The analysis reveals that the curvature factor is more informative about the future evolution of the yield curve and of economic activity than has previously been acknowledged. The fourth essay provides a monthly business cycle chronology for the Euro area. A monthly series of Euro area real GDP is constructed using an interpolation routine that nests previously suggested approaches as special cases. Then, a dating routine is applied to the interpolated series which excludes business cycle phases that are short and flat.
248

InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors

Tran, Lien 21 June 2011 (has links)
Im Rahmen dieser Arbeit wurden InSb- und verdünnt-magnetische In_{1-x}Mn_xSb Filme mittels Gasquellen-Molekularstrahlepitaxie hergestellt und deren strukturelle und elektronische Eigenschaften untersucht. Die 2 μm InSb-Dünnschichten wurden sowohl auf GaAs(001)-Substrat als auch um 4° in Richtung [110] fehlgeschnittenem Si(001)-Substrat hergestellt. Optimierte InSb-Schichten direkt auf GaAs zeigen eine hohe kristalline Qualität, niedriges Rauschen und eine Elektronenbeweglichkeit von 41100 cm^2/Vs bei 300 K. Die Ladungsträgerkonzentration beträgt etwa 2,9e16 cm^{-3}. Um InSb-Dünnschichten guter Qualität auf Si-Substrat zu realisieren, wurden fehlgeschnittene Substrate benutzt. Zur Reduzierung der Gitterfehlanpassung wurden Pufferschichten gewachsen. Eine Elektronenmobilität von 24000 cm^2/Vs und Ladungsträgerkonzentration von 2,6e16 cm^{-3} wurden bei 300 K nachgewiesen. Diese Probe enthält ein 0,06 μm GaAs/AlSb-Supergitter als Pufferschicht (Wachstumstemperatur war 340°C). Diese Probe zeigt der höheren Dichte der Microtwins und Stapelfehler als auch den Threading-Versetzungen in der schnittstellennahen Region geschuldet. Die Deep-Level Rauschspektren zeigen die Existenz von Deep-Levels sowohl in GaAs- als auch in Si-basierten Proben. Die InSb-Filme auf Si-Substrat zeigen einen kleineren Hooge-Faktor im Vergleich zu Schichten auf GaAs (300 K). Unter Anwendung der optimierten Wachstumsbedingungen für InSb/GaAs wurden verdünnt-magnetische In_{1-x}Mn_xSb-Schichten (bis zum 1% Mangan) auf GaAs (001)-realisiert. Mn verringert die Gitterkonstante und damit den Grad der Relaxation von (In,Mn)Sb-Filmen. In den Proben befindet sich Mn in zwei magnetischen Formen, sowohl als verdünnt-magnetischer Halbleiter (In,Mn)Sb, als auch als MnSb-Cluster. Die Cluster dominieren auf der Oberfläche. Die Curie-Temperatur, Tc, unterscheidet sich für die beiden Formen. Für (In,Mn)Sb ist Tc kleiner als 50 K. Die MnSb-Cluster zeigen dagegen ein Tc über 300 K. / This dissertation describes the growth by molecular beam epitaxy and the characterization of the semiconductor InSb and the diluted magnetic semiconductor (DMS) In_{1-x}Mn_xSb. The 2 µm-thick InSb films were grown on GaAs (001) substrate and Si (001) offcut by 4° toward (110) substrate. After optimizing the growth conditions, the best InSb films grown directly on GaAs results in a high crystal quality, low noise, and an electron mobility of 41100 cm^2/V s Vs with associated electron concentration of 2.9e16 cm^{-3} at 300 K. In order to successfully grow InSb on Si, tilted substrates and the insertion of buffer layers were used. An electron mobility of 24000 cm^2/V s measured at 300 K, with an associated carrier concentration of 2.6e16 cm^{-3} is found for the best sample that was grown at 340°C with a 0.06 μm-thick GaSb/AlSb superlattice buffer layer. The sample reveals a density of microtwins and stacking faults as well as threading dislocations in the near-interface. Deep level noise spectra indicate the existence of deep levels in both GaAs and Si-based samples. The Si-based samples exhibit the lowest Hooge factor at 300 K, lower than the GaAs-based samples. Taking the optimized growth conditions of InSb/GaAs, the DMS In_{1-x}Mn_xSb/GaAs is prepared by adding Mn (x < 1%) into the InSb during growth. Mn decreases the lattice constant as well as the degree of relaxation of (In,Mn)Sb films. Mn also distributes itself to result in two different and distinct magnetic materials: the DMS (In,Mn)Sb and clusters MnSb. The MnSb clusters dominate only on the surface. For the DMS alloy (In,Mn)Sb, the measured values of Curie temperature Tc appears to be smaller than 50 K, whereas it is greater than 300 K for the MnSb clusters.
249

Essays on foreign aid and macro-economic performance of Sub-Saharan African countries

Saleh, Omar 01 May 2019 (has links)
Foreign aid is a major flow of income into sub-Saharan African (SSA) countries, averaging roughly 12% of GDP over the last four decades. Yet, SSA countries are characterized by very low per capita output, low human capital attainment, and widespread poverty. This dissertation investigates the macroeconomic and welfare effects of foreign aid to SSA countries. The empirical part of the dissertation studies 22 SSA countries, and uses a cointegrated vector autoregressive analysis (CVAR). This methodology identifies long-run effects without imposing strong statistical priors. I introduce tradable and non-tradable sectors into the analysis to determine if the so-called “Dutch Disease” is the reason for the plight of SSA countries. “Dutch Disease” occurs when a positive shock to foreign aid perversely reduces GDP, by decreasing the relative price of tradable to nontradable goods, thus reducing the size of the tradable sector. While I find that aid reduces GDP in eight countries, this result is inconsistent with the “Dutch Disease” as it is not accompanied by large relative price changes. The analysis controls for a number of country-specific characteristics including extraordinary events. Overall, I find non-positive impacts of foreign aid on GDP and the tradable sector, with a few exceptions. I also consider the reverse causal channel and test whether country-specific macroeconomic variables drive foreign aid flows. I find that GDP, tradable output, and tradable and non-tradable goods prices do affect the amount of aid a country receives in 15 countries. These variables have no impact on foreign aid (aid is considered as weakly exogenous) in six countries. The theoretical part of the dissertation develops two dynamic stochastic general equilibrium — real business cycle — (DSGE-RBC) models to analyze the effects of foreign aid on human capital investment and the business cycle. The distinguishing feature of the models is to embed a human capital investment in a small open economy model of Mendoza (1991). The first model considers one-sector DSGE model, which is followed by two-sector (tradable and non-tradable) DSGE model. Both models distinguish between physical and human capital investment and allow for labor-leisure choice. In the analysis, labor supply and time spent studying or acquiring skills are optimally chosen. The models are calibrated to match the key features of the Kenyan economy. In both models, a positive aid shock initially has a negative impact on labor supply and output. However, the shock subsequently has a positive effect on physical and human capital investment, and time spent studying. This is due to a positive income effect from the shock. A rise in foreign aid increases consumption; consumption smoothing across periods raises physical and human capital investment, labor productivity, and output. I also find that reducing the volatility of aid has a significant positive effect on human capital investment and welfare. Policymakers should focus on reducing the volatility of foreign aid and not solely concentrate on the average level of aid. The analysis of the two-sector DSGE-RBC model incorporates the role for the “Dutch Disease” mechanism. Consistent with the “Dutch Disease”, I find that a shock to foreign aid appreciates the relative price of non-tradable goods that causes the factors of production to reallocate from the tradable sector to the non-tradable sector, leading to a decline in GDP and the tradable output. Finding the “Dutch Disease” result here is not necessarily at odds with the CVAR estimation results as the DSGE-RBC simulation is a short-run analysis and the CVAR estimation is a long-run analysis. / Graduate
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台灣股價與景氣循環關係之研究

高崇傑, Kao, Chung-Chieh Unknown Date (has links)
股票市場乃屬長期資本市場,企業家透過「資本證券化」的方式向投資人募集資金,做為公司營運及擴充規模之用。是故股票市場繫乎一國的經濟發展,乃經濟發展之櫥窗。無論基於何種因素,股價確實會有漲跌互異的現象,但消息面、心理面或其他非經濟因素並不能完全的支配股價走勢,從長期而論,股價終究會回歸基本面,所謂基本面,就是經濟之榮枯,常以景氣的好壞來表現,景氣循環即為一種經濟波動的現象。是故,雖致使股價波動的因素繁多,然而由長期基本面的觀點來看,景氣循環是否為解釋台灣股價指數長期走勢的主要力量呢?此乃本文所欲探尋的答案。本文以經建會所公佈之景氣領先指標綜合指數及其組成要素分別代表景氣狀況,從理論與文獻上整理說明股價變動與景氣循環的關係,並陳述1990年代的台灣股價指數與景氣循環走勢之關係,最後利用由Johansen所發展非常適於經濟模型的估計與檢定的計量工具---共整合分析與向量誤差修正模型,企圖以變數間所具有的整合線性關係作為衡量長期的均衡關係,並以均方誤差(RMSE)與絕對平均百分比誤差(MAPE)評量預測績效。 本文最終實證所得之各項重要結論如下: 一、股價與領先指標綜合指數 短期上落後一期和落後四期的領先指標綜合指數變動率與股價報酬率具有顯著的正向關係,此外股價與領先指標綜合指數長期存在正向共整合方程式。 二、股價與貨幣供給M1b具正向關係 長期而言依據共整合檢定,兩者具有長期均衡關係,並在同期時具顯著正向關係;在短期方面,依誤差修正模型之t檢定當期股價報酬率與落後一期之貨幣供給變動率呈現顯著正相關。 三、股價與海關出口值、新接訂單指數 股價分別在長期與兩者具均衡關係,並在同期時具顯著正向關係,但在短期上並無明顯關係。 四、股價與躉售物價、製造業平均每人每月工時、台灣地區房屋建築申請面積並無明顯關係。 五、所有五個共整合模型之預期值,均顯示出在上升波段預期值低於股價實際值,而在下跌波段預期值高於股價,此明顯反應了台灣股市投資人較不重視基本面分析,而以短線操作為主,心理因素、炒作因素影響重大,所以經濟景氣時常一窩峰買進而高估股價,反之,則大量殺出而低估股價。 六、五項共整合模型預期績效之良劣順序為:1.領先指標綜合指數與股價之ECM;2.三領先變數綜合與股價之ECM;3.M1b與股價之ECM;4.製造業新接訂單與股價之ECM;5.海關出口值之ECM由上面之順序顯示考量較多經濟變數較能涵蓋實質經濟,也能獲致較佳之預期。 總合而言,本研究各項模型雖不盡如人意,但對於大盤走勢之預期有不錯之效果,若再加入國人之心理因素,於牛市中將預期值往上修正,而於熊市將預期值往下修正,本模型應可更貼近實際股市情況。

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