The application of different unit root statistics is by now a standard practice in empirical work. Even when it is a practical issue, these statistics have complex nonstandard distributions depending on functionals of certain stochastic processes, and their derivations represent a barrier even for many theoretical econometricians. These derivations are based on rigorous and fundamental statistical tools which are not (very) well known by standard econometricians. This paper aims to fill this gap by explaining in a simple way one of these fundamental tools: namely, the Functional Central Limit Theorem. To this end, this paper analyzes the foundations and applicability of two versions of the Functional Central Limit Theorem within the framework of a unit root with a structural break. Initial attention is focused on the probabilistic structure of the time series to be considered. Thereafter, attention is focused on the asymptotic theory for nonstationary time series proposed by Phillips (1987a), which is applied by Perron (1989) to study the effects of an (assumed) exogenous structural break on the power of the augmented Dickey-Fuller test and by Zivot and Andrews (1992) to criticize the exogeneity assumption and propose a method for estimating an endogenous breakpoint. A systematic method for dealing with efficiency issues is introduced by Perron and Rodriguez (2003), which extends the Generalized Least Squares detrending approach due to Elliot et al. (1996). An empirical application is provided. / Hoy en día es una práctica estándar de trabajo empírico la aplicación de diferentes estadísticos de contraste de raíz unitaria. A pesar de ser un aspecto práctico, estos estadísticos poseen distribuciones complejas y no estándar que dependen de funcionales de ciertos procesos estocásticos y sus derivaciones representan una barrera incluso para varios econometristas teóricos. Estas derivaciones están basadas en herramientas estadísticas fundamentales y rigurosas que no son (muy) bien conocidas por econometristas estándar. El presente artículo completa esta brecha al explicar en una forma simple una de estas herramientas fundamentales la cual es el Teorema del Límite Central Funcional. Por lo tanto, este documento analiza los fundamentos y la aplicabilidad de dos versiones del Teorema del Límite Central Funcional dentro del marco de una raíz unitaria con un quiebre estructural. La atención inicial se centra en la estructura probabilística de las series de tiempo propuesta por Phillips (1987a), la cual es aplicada por Perron (1989) para estudiar los efectos de un quiebre estructural (asumido) exógeno sobre la potencia de las pruebas Dickey-Fuller aumentadas y por Zivot y Andrews (1992) para criticar el supuesto de exogeneidad y proponer un método para estimar un punto de quiebre endógeno. Un método sistemático para tratar con aspectos de eficiencia es introducido por Perron y Rodríguez (2003), el cual extiende el enfoque de Mínimos Cuadrados Generalizados para eliminar los componentes determinísticos de Elliot et al. (1996). Se presenta además una aplicación empírica.

Regression discontinuity designs are increasingly popular quasi-experimental research designs among applied econometricians desiring to make causal inferences on the local effect of a treatment, intervention, or policy. They are also widely used in social, behavioral, and natural sciences. Much of the existing literature relies on the assumption that the discontinuity point or cutoff is known a-priori, which may not always hold. This thesis seeks to extend the applicability of regression discontinuity designs by proposing a new approach towards detection of an unknown discontinuity point using structural-break detection and machine learning methods. The approach is evaluated on both simulated and real data. Estimation and inference based on estimating the cutoff following this approach are compared to the counterfactual scenario where the cutoff is known. Monte Carlo simulations show that the empirical false-detection and true-detection probabilities of the proposed procedure are generally satisfactory. Finally, the approach is further illustrated with an empirical application. / Graduate

<p> The overall theme of my dissertation is applying frontier econometric models to interesting economic problems. The first chapter analyzes how individual consumption responds to permanent and transitory income shocks is limited by model misspecification and availability of data. The misspecification arises from ignoring unemployment risk while estimating income shocks. I employ the Heckman two step regression model to consistently estimate income shocks. Moreover, to deal with data sparsity, I propose identifying the partial consumption insurance and income and consumption volatility heterogeneities at the household level using Least Absolute Shrinkage and Selection Operator (LASSO). Using PSID data, I estimate partial consumption insurance against permanent shock of 63% and 49% for white and black household heads, respectively; the white and black household heads self-insure against 100% and 90% of the transitory income shocks, respectively. Moreover, I find income and consumption volatilities and partial consumption insurance parameters vary across time. In the second chapter I recast smooth structural break test proposed by Chen and Hong (2012), in a predictive regression setting. The regressors are characterized using the local to non-stationarity framework. I conduct a Monte Carlo experiment to evaluate the finite sample performance of the test statistic and examine an empirical example to demonstrate its practical application. The Monte Carlo simulations show that the test statistic has better power and size compared to the popular SupF and LM. Empirically, compared to SupF and LM, the test statistic rejects the null hypothesis of no structural break more frequently when there actually is a structural break present in the data. The third chapter is a collaboration with James Reeder III. We study the effects of using promotions to drive public policy diffusion in regions with polarized political beliefs. We estimate a model that allows for heterogeneous effects at the county-level based upon state-level promotional offerings to drive vaccine adoption during COVID-19. Central to our empirical application is accounting for the endogenous action of state-level agents in generating promotional schemes. To address this challenge, we synthesize various sources of data at the county-level and leverage advances in both the Bass Diffusion model and 10 machine learning. Studying the vaccine rates at the county-level within the United States, we find evidence that the use of promotions actually reduced the overall rates of adoption in obtaining vaccination, a stark difference from other studies examining more localized vaccine rates. The negative average effect is driven primarily by the large number of counties that are described as republican leaning based upon their voting record in the 2020 election. Even directly accounting for the population’s vaccine hesitancy, this result still stands. Thus, our analysis suggests that in the polarized setting of the United States electorate, more localized policies on contentious topics may yield better outcomes than broad, state-level dictates. </p>

本研究共包含三篇論文，首先修正von Hagen and Hepp(2000)所建立模型分析政府的財源轉移之風險分散與重分配動態效果。整體而言，補助與協助收入或統籌分配款所產生的所得與稅收風險分散或重分配效果相當有限，且各分區(北、中、南與全區)的結論差異甚大，顯示財源轉移發揮的效率不足。統籌分配款對於改善稅收的風險分散與重分配上，效果優於補助與協助收入。各縣市取得的補助與協助收入或統籌分配款高於長期所得與稅收風險分散與重分配所應對應的額度，造成資源浪費。就全區而言，前幾期稅收(所得)風險分散變化，可作為短期調整補助與協助收入(統籌分配款)的依據；統籌分配款與稅收的風險分散、補助與協助收入或統籌分配款與稅收重分配均存在雙向因果關係。 其次，在分析勞動者的休閒時間選擇時，本文修正跨期選擇模型，考慮勞動者持有投資組合與採取避險措施，並面對租稅問題下，以導出休閒時間方程式。實證上採用混合估計法針對12種樣本產業及兩種不同休閒時間衡量方式進行估計，結果顯示不同休閒時間衡量方式，影響估計結果甚鉅；金融市場的變化與波動攸關休閒時間變動：國內外利率、匯率與遠期匯率等與投資組合報酬相關的變數，在多數情況下顯著地影響休閒時間變動，且各變數對於休閒時間的影響程度，在工業中的次級產業大於服務業中的次產業。此外，採行周休二日制度確實改變制度採行前後的休閒時間，惟在三個工業次產業上則不明顯。 最後，修正Bo and Sterken (2002) 所建立的最適動態模型，分析公司價值不確定與租稅措施對海運廠商投資的影響，經由最大化公司價值導出影響台灣海運公司投資的三種不確定來源與避險措施，並進行實證估計。實證結果顯示，不確定的衡量方式攸關投資函數的估計結果，以指數加權移動平均標準差衡量不確定時，其估計結果優於以GARCH(1,1)衡量不確定，隱含廠商較在乎可預期波動對投資的影響。一般而言，廠商利率與原油價格的波動增加，均不利於公司投資，其中以原油價格不確定對於投資的影響最大，其效果約略與廠商利率相當。其次，影響海運公司投資最重要的三項因素均分別為BDI、負債與廠商利率，顯示價格與債務規模的重要性更甚於利率。此外，三種公司價值不確定來源對投資的影響，在多數個別公司之間並無顯著的差異，有助於採行總體財金政策以刺激投資。 / This dissertation contains three articles. First I revise the models set up by von Hagen and Hepp (2000) to analyze the dynamic effects of the Aid and Assistance and central government’s Tax Redistribution Fund on income (or tax) risk sharing and redistribution. For all the counties in Taiwan area the effects are tiny, but those are diverse among the counties in each Taiwan sub-area. The Aid and Assistance and central government’s Tax Redistribution Fund actually obtained by each county are larger than the amounts required to maintain long-term risk sharing and redistribution effects. These all imply that fiscal transfer is inefficiency. The effects of the central government’s Tax Redistribution Fund on risk sharing and redistribution are larger than those of Aid and Assistance. The central government can adjust the Aid and Assistance based on the change of earlier-period ax (income) risk sharing effect. Moreover, the existence of significant short-run interaction between the central government’s Tax Redistribution Fund and tax risk sharing, the Aid and Assistance and tax redistribution. Secondly, I revise intertemporal choice model by considering portfolio selection, hedging and taxation problems to derive economic agent’s leisure time equation. In empirical study, we focus on twelve sample industries and two different leisure time measurements, then adopt pooled estimation to estimate leisure time equation. Empirical results show that different measurement of leisure time influences estimation outcomes tremendously. Furthermore, the financial variables affecting portfolio return, including domestic and foreign interest rates, exchange rate and forward rate almost have remarkable effect on leisure time. Finally, the effect of each explanatory variable on leisure time is larger in industry than in service industry. Finally, I revise the optimal intertemporal model, constructed by Bo and Sterken (2002), by maximizing corporate value to derive three uncertainty sources and hedging influencing shipping-firm investment. Empirical evidences show that it is relevant for the estimation results to adopt which methods to measure the uncertainty. The outcomes derived from taking the Exponential Weighted Moving Average model to measure uncertainty are better than those from adopting the GARCH(1,1) model. Generally, as the volatilities in firm’s interest rate and crude oil price increase, firm investment decreases and the effect of crude oil price uncertainty on investment, the largest among the four effects, is nearly equal to that of firm interest rate on investment. Furthermore, BDI, debt and firm interest rate are the most important variables influencing firm investment. Finally, the effects of three uncertainty sources on investment are almost indifferent among the ten shipping-firms.

[pt] Estimamos um modelo DSGE para a economia brasileira abrangendo a transição do regime de bandas cambiais para o regime de metas para a inflação ocorrida em 1999. Utilizamos um modelo novo keynesiano de pequena economia aberta no qual o Banco Central segue uma regra de política monetária estruturalmente distinta em cada regime. Encontramos diferenças significativas na dinâmica macroeconômica e nos mecanismos de transmissão dos choques estruturais, com destaque àqueles relacionados ao setor externo da economia. Realizamos experimentos contrafactuais onde simulamos o impacto de cenários alternativos para a transição de regime na trajetória das variáveis econômicas brasileiras. Entre outros resultados, as simulações sugerem que a manutenção do sistema de bandas cambiais seria insustentável enquanto a antecipação da implementação do regime de metas para a inflação para antes da crise da Rússia de 1998 poderia deixar a economia brasileira em situação mais favorável. Por fim, mostramos que um teste de quebra estrutural aplicado sobre todo o período amostral detecta com precisão a ocorrência da mudança de regime em 1999. / [en] We estimate a DSGE model of the brazilian economy taking into account the transition from the exchange rate band system to inflation targeting occurred in 1999. We use a new Keynesian small open economy model where the Central Bank follows structurally different monetary policy rules in each regime. By comparing the transmission channels of exogenous shocks we find significant differences across the regimes, specially on those shocks related to the foreign sector of the economy.We then perform counterfactual experiments where we simulate the response of key macro variables under alternative scenarios for the regime transition. Among other results our simulations suggest that the continuation of the exchange rate band system could have been unsustainable while anticipating the transition to inflation targeting before the Russian crisis of 1998 could have benefited the economy. Additionally, we show that a structural break test applied to the whole data sample correctly identifies the regime change in 1999.

Submitted by Ary Cera Zanetta Neto Zanetta (ary.zanetta@brasil-capital.com) on 2014-08-19T19:21:54Z No. of bitstreams: 1 Efeitos de Choques Globais na Economia Brasileira_ Uma Análise a Partir do GVAR.pdf: 1085836 bytes, checksum: 25e953aa352fed09b5b828362226aab9 (MD5) / Rejected by JOANA MARTORINI (joana.martorini@fgv.br), reason: A ficha catalográfica não está valida, por gentileza aguardar o envio da ficha correta pala biblioteca digital. on 2014-08-19T19:29:14Z (GMT) / Submitted by Ary Cera Zanetta Neto Zanetta (ary.zanetta@brasil-capital.com) on 2014-08-19T20:33:33Z No. of bitstreams: 1 Efeitos de Choques Globais na Economia Brasileira_ Uma Análise a Partir do GVAR.pdf: 1085836 bytes, checksum: 25e953aa352fed09b5b828362226aab9 (MD5) / Approved for entry into archive by JOANA MARTORINI (joana.martorini@fgv.br) on 2014-08-20T16:30:59Z (GMT) No. of bitstreams: 1 Efeitos de Choques Globais na Economia Brasileira_ Uma Análise a Partir do GVAR.pdf: 1085836 bytes, checksum: 25e953aa352fed09b5b828362226aab9 (MD5) / Made available in DSpace on 2014-08-20T19:02:31Z (GMT). No. of bitstreams: 1 Efeitos de Choques Globais na Economia Brasileira_ Uma Análise a Partir do GVAR.pdf: 1085836 bytes, checksum: 25e953aa352fed09b5b828362226aab9 (MD5) Previous issue date: 2014-08-05 / O objetivo deste estudo é avaliar a propagação de choques econômicos de alguns países sobre o crescimento econômico brasileiro, com principal destaque para China, Estados Unidos da América (EUA) e Argentina, que são os principais parceiros comerciais do Brasil. O aumento do comércio com a China tornou o Brasil muito mais vulnerável a choques no PIB chinês e menos vulnerável, do que no passado recente, a choques no PIB americano, enquanto que a influência da Argentina manteve-se estável. Foi aplicada a metodologia Vetor Autorregressivo Global (Global Var – GVAR), introduzida por Pesaran, Schuermann e Weiner (2004), Garratt, Lee, Pesaran e Shin (2006) e Dées, Di Mauro, Pesaran e Smith (2007), para analisar os canais de comércio e a transmissão de choques entre o resto do mundo e o Brasil. Usando dados trimestrais a partir de 1990 até o final de 2013, foi possível constatar que o aumento da relevância da economia Chinesa na balança comercial Brasileira exerce pressão sobre o crescimento econômico do Brasil. Em suma, a China tornou-se mais relevante para o crescimento econômico do Brasil do que os EUA e a Argentina. / The objective of this study is to evaluate the impact of variations in the Gross Domestic Product (GDP) of countries and economic blocks over Brazilian economic growth, with emphasis on China, United States of America (USA) and Argentina, which are the main commercial partners of Brazil. The increase in trading with China has made Brazil more vulnerable to shocks in Chinese GDP and less vulnerable, than in the recent past, to shocks in American GDP, and stability in the case of Argentina. It has been applied the methodology Global Vector Autorregressive (Global Var – GVAR), introduced, explained and expanded by Pesaran, Schuermann and Weiner (2004), Garratt, Lee, Pesaran and Shin (2006) and Dées, Di Mauro, Pesaran and Smith (2007) to analyze the trading channels and the transmission of shocks between the rest of the world and Brazil (specially with China, USA and Argentina). Using a sample from the first quarter of 1990 to the third quarter of 2013 it is possible to see that the increase of relevance of the Chinese economy on the Brazil trade balance increased the relevance of the Chinese economy over the Brazilian economy. Therefore, the conclusions of this work indicate a considerable vulnerability of the Brazilian economy to the Chinese economic cycle and, in a lower degree than in the past, to the American and Argentinian economies.

Submitted by Bernardo Antunes Maciel Villela (bernardovillela@gmail.com) on 2015-02-11T02:28:23Z No. of bitstreams: 1 Tese_versao_final_Bernardo_Villela.pdf: 977767 bytes, checksum: fdf2c1c96387a401d0ee81c883965af9 (MD5) / Approved for entry into archive by GILSON ROCHA MIRANDA (gilson.miranda@fgv.br) on 2015-03-06T19:04:46Z (GMT) No. of bitstreams: 1 Tese_versao_final_Bernardo_Villela.pdf: 977767 bytes, checksum: fdf2c1c96387a401d0ee81c883965af9 (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2015-03-12T19:40:11Z (GMT) No. of bitstreams: 1 Tese_versao_final_Bernardo_Villela.pdf: 977767 bytes, checksum: fdf2c1c96387a401d0ee81c883965af9 (MD5) / Made available in DSpace on 2015-03-12T19:41:05Z (GMT). No. of bitstreams: 1 Tese_versao_final_Bernardo_Villela.pdf: 977767 bytes, checksum: fdf2c1c96387a401d0ee81c883965af9 (MD5) Previous issue date: 2014-05-30 / The automotive sector is fairly representative in the national economy, which motivated this study on the demand for new vehicles in Brazil. The present work discusses an econometric model which allows the calculation of the price, income and credit elasticities on the demand for vehicles in the light of the cointegration theory. Analyzing the period from June 2000 to January 2014, it is possible to observe three structural breaks. These breaks divide the time interval analyzed in four sub-periods, each with its own dynamics. The perception of this fact often overlooked in previous literature is one of the main findings of this work. In fact, very different conclusions would be obtained by considering the entire period without breaks. It is also worth noting that credit has been relevant to the demand in all sub-periods. Therefore, it seems to be effective to implement a policy to boost the automotive sector by encouraging credit. Finally, it is said that in recent history for each 1% reduction in car price, demand has increased in a 30% higher rate. This result corroborates the perception that tax cuts may boost the sale of vehicles. / O setor automotivo é bastante representativo na economia nacional, o que motivou a realização deste estudo sobre a demanda por veículos novos no Brasil. No presente trabalho, é abordado um modelo econométrico que permite calcular as elasticidades do preço, da renda e do crédito em relação à demanda por veículos, sob a luz da teoria da cointegração. Analisando-se o período de junho de 2000 a janeiro de 2014, verifica-se a ocorrência de três quebras estruturais. Estas quebras dividem o intervalo de tempo analisado em quatro subperíodos, cada um com uma dinâmica própria. A constatação deste fato, muitas vezes negligenciado na literatura científica prévia, é um dos principais resultados deste trabalho: afinal, conclusões bastante distintas seriam obtidas ao se considerar o período todo sem quebras. Vale também destacar que o crédito se mostrou relevante para a demanda em todos os subperíodos: acredita-se, portanto, ser efetiva a implementação de uma política de estímulo ao setor, por meio do incentivo ao crédito. Por último, comenta-se que, no passado recente, a cada 1% de redução no preço do automóvel, a demanda aumentou numa proporção 30% maior. Este resultado corrobora com a percepção de que a redução de impostos pode alavancar a venda de veículos.

Made available in DSpace on 2017-07-10T18:33:20Z (GMT). No. of bitstreams: 1 Ariana Cericatto da Silva.pdf: 5534687 bytes, checksum: 4364b3464e3d77d3a370755413e48d94 (MD5) Previous issue date: 2014-12-08 / This research analyzed the structural rupture process of Paraná regional economy, between 1985 to 2012. It searchs to understand the process of growth, transformation and diversification of the regional economy of the State of Paraná, and analyze the changes in the structure of the economy and how micro-regions and economic sectors behaved and influenced the development of micro-regions. The theoretical contributions was used to discuss how regional development happens and how economies develop and make changes in their sectoral structures. Completing this line of study, was used as methodology, the methods of regional analysis through tracing vital statistics and regional measures, the variable bas was the formal employment which could show the hand of behavior of the labor over the analysis period and it was possible to diagnose the moment that the process of structure breakdown has occurred in the micro-regions of Paraná. The results demonstrate that the State of Paraná has done important changes in their sectoral structure. In the analyzed period, from 1985 to 2012, most of the state's micro-regions showed hard concentration of formal employment in the primary sector of the economy. Therefore, it proves that this sector continues to be representative to the state and that some of the micro-regions had not passed or completed their structural rupture process. However, in relation to the structural rupture process, it was detect that some micro of Paraná had a strong concentration of formal employment in the secondary sector before 1985, showing that its structural rupture process occurred in the previous period. In 1992, there was the spreading of the secondary sector leading the process of structural break for the latest occupations areas. So, it concludes that, for the State of Paraná, the tertiary sector has contributed with the rupture process, because it understands that many tertiary activities emerge as auxiliary secondary of the primary activities. Regarding the productive restructuring the biggest changes occurred at the first period 1985/1999, after this, the production restructuring decreased intensity in the state of Paraná. Therefore, it understands that the knowledge about the characteristics and configuration of economic sectors in geographic micro-regions of Paraná contributes to the government in carrying out activities that can improve the economic organization of the spaces, as well as for society in decision-making, contributing for the development of the state as a whole. / Essa pesquisa analisou o processo de ruptura estrutural da economia regional paranaense, no período de 1985 a 2012. Buscou-se compreender o processo de crescimento, transformação e diversificação da economia regional do Estado do Paraná e analisar as mudanças na estrutura da economia e como as microrregiões e setores econômicos se comportaram e influenciaram no desenvolvimento das microrregiões. Para isso, utilizaram-se as contribuições teóricas que discutem como o desenvolvimento regional acontece e como as economias se desenvolvem e passam por transformações nas suas estruturas setoriais. Completando essa linha de estudo, utilizaram-se como metodologia os métodos de análise regional através das medidas de localização e medidas regionais, a variável-base utilizada foi o emprego formal que conseguiu demonstrar o comportamento da mão de obra ao longo do período de análise e assim foi possível diagnosticar o momento em que o processo de ruptura estrutural ocorreu nas microrregiões paranaenses. Os resultados demonstraram que o Estado do Paraná passou por transformações importantes na sua estrutura setorial. No período analisado, 1985 a 2012, a maioria das microrregiões paranaenses apresentaram forte concentração de emprego formal no setor primário da economia. Com isso, comprova-se que este setor continua sendo representativo para o Estado e que algumas microrregiões ainda não passaram ou concluíram seu processo de ruptura estrutural. No entanto, em relação ao processo de ruptura estrutural constatou-se que algumas microrregiões paranaenses apresentavam forte concentração de emprego formal no setor secundário antes de 1985, demostrando que seu processo de ruptura estrutural ocorreu em período anterior. Em 1992 ocorreu o espraiamento do setor secundário levando o processo de ruptura estrutural para áreas de ocupações mais recentes. Conclui-se que para o Estado do Paraná o setor terciário contribuiu para que o processo de ruptura acontecesse, pois se entende que muitas atividades terciárias surgem como auxiliares das atividades secundárias e primárias. Em relação à reestruturação produtiva as maiores mudanças ocorreram no primeiro período 1985/1999, depois disso a reestruturação produtiva diminuiu de intensidade no Estado do Paraná. Portanto, entende-se que conhecer as especificidades e a configuração dos setores econômicos nas microrregiões geográficas do Paraná contribui para o poder público na execução de ações que possam melhorar as organizações econômicas do espaço, bem como, para a sociedade na tomada de decisões, contribuindo para o desenvolvimento do Estado como um todo.

Cette thèse est une contribution empirique à l’analyse du commerce des produits alimentaires entre le Cameroun et les pays voisins de la zone CEMAC et le Nigeria. La thèse utilise plusieurs outils économétriques permettant de mieux prendre en compte le niveau de désagrégation des données par produits et paires de marchés agricoles. Le premier chapitre, essentiellement descriptif, présente quelques faits stylisés sur le commerce intra-régional en zone CEMAC. Le deuxième chapitre analyse la contribution des chocs de rente pétrolière dans les pays limitrophes du Cameroun sur leur demande d’importations de produits alimentaires camerounais. En utilisant une variété d’estimateurs appropriés pour les modèles de gravité, les résultats indiquent que la croissance de la rente pétrolière dans la sous-région a favorisé de manière significative, l’expansion des exportationscamerounaises de produits alimentaires. Le troisième chapitre a pour objectif d’apprécier l’existence de ruptures structurelles et le degré d’asymétrie dans le niveau d’intégration des marchés agricoles au Cameroun. Les résultats des estimations des modèles à correction d’erreur avec rupture et asymétriques révèlent l’existence d’une instabilité temporelle récente dans l’intégration des marchés agricoles au Cameroun. De plus, les résultats indiquent que les chocs de prix de certains produits agricoles dans les marchés de consommation répondent de façon asymétrique aux variations des prix des marchés de production. Enfin, le quatrième chapitre utilise un modèle à deux pays pour quantifier le degré d’intégration entre les marchés camerounais et sous-régionaux (Gabon) au prisme d’une analyse de co-mouvement des prix des entre marchés. Les résultats économétriques obtenus à partir d’estimation de modèles vectoriels à correction d’erreur sur données de panel montrent qu’il existe une causalité bidirectionnelle et positive à court et long terme entre les marchés camerounais et gabonais. / This is an empirical contribution to the analysis of the regional integration of agricultural markets in central Africa. The thesis uses several econometric models aimed at taking advantage of the high disaggregation of the data by products and market dyads. The first chapter focuses on recent stylized facts on agricultural trade and food security in Cameroon and in the region. Chapter 2 examines the effect of oil discoveries in neighbor countries on Cameroonian exports of agricultural products within the region. Using a wide range of estimators designed for gravity data, econometric results uncover a positive and significant association between oil discoveries in neighbor regional countries on the demand for Cameroonian agricultural goods. The third chapter tests and discusses the existence of a temporal structural break and the asymmetry in agricultural markets within Cameroon. The econometric results obtained from error correction models allowing for structural break and the asymmetry of shocks show that Cameroonian agricultural markets have become less integrated recently, contributing to the asymmetry in the transmission of shocks from production to consumption markets. Chapter 4 uses a two-country model to provide an international evidence of the integration of agricultural markets in central Africa. The framework consists in estimating vector error correction models usingpanel data to test the causality between product prices between the two countries. The results highlight the existence of a bi-directional causality in both the short and long-run.

[pt] A teoria moderna de carteiras estabelece que a alocação ótima de ativos é uma função da média-variância da distribuição dos retornos. Na prática, estes retornos são modelados por distribuições Gaussianas e seus parâmetros são estimados a partir dos dados históricos do mercado, utilizando técnicas descritivas da estatística Frequentista. A dinâmica atual dos mercados globalizados gera períodos aleatórios de alta e baixa volatilidade e/ou saltos nos retornos dos ativos, provocando mudanças de regime ou quebras estruturais na série temporal dos retornos, tornando-os não Gaussianos. Consequentemente, a teoria moderna de carteiras precisa ser adaptada para atender a estas novas condições do mercado. Para contornar o problema das mudanças de regime, propõe-se a substituição do mecanismo de otimização baseada no índice de Sharpe pela otimização baseada na medida Ômega. Isto porque a medida Ômega tem a vantagem de quantificar o risco-retorno de qualquer distribuição de probabilidade e não somente distribuições Gaussianas como acontece com o índice de Sharpe, ou seja, as distribuições de retornos não Gaussianos provocadas pelas mudanças de regime são tratadas naturalmente pela medida Ômega. Para contornar o problema das quebras estruturais, propõe-se a substituição do procedimento de estimação dos parâmetros da distribuição dos retornos, baseada em técnicas da estatística Frequentista por técnicas da estatística Bayesiana. Isto porque a estatística Bayesiana, tem a vantagem de combinar as informações públicas do mercado (dados históricos dos retornos) com informações privadas do investidor (visões prospectivas do mercado) permitindo corrigir a quebra estrutural e, na sequência, tratar o retorno não Gaussiano, utilizando o mecanismo de otimização baseada na medida Ômega. / [en] Modern portfolio theory states that the optimal asset allocation is a function of the mean-variance of the distribution of returns. In practice, these returns are modeled by Gaussian distributions and their parameters are estimated from historical market data, using descriptive techniques of Frequentist statistics. The current dynamics of globalized markets generate random periods of high and low volatility and/or jumps in asset returns, causing regime shifts or structural breaks in the time series of returns, making them non Gaussian. Consequently, modern portfolio theory needs to be adapted to meet these new market conditions. To circumvent the problem of regime shifts, it is proposed to replace the optimization mechanism based on the Sharpe index by the optimization based on the Omega measure. This is because the Omega measure has the advantage of quantifying the risk-return of any probability distribution and not only Gaussian distributions as with the Sharpe index, that is, non Gaussian returns distributions caused by regime shifts are treated naturally by the Omega measure. To circumvent the problem of structural breaks, it is proposed to replace the estimation procedure for the parameters of the distribution of returns, based on Frequentist statistics techniques, by Bayesian statistical techniques. This is because the Bayesian statistic has the advantage of combining public market information (historical return data) with private investor information (prospective market views) allowing to correct the structural break, and subsequently, treating the non Gaussian return using the optimization based on the Omega measure.