The inequality accelerator

We show that the transition from an economy characterized by idiosyncratic income shocks and incomplete markets a la Aiyagari (1994) to markets where statecontingent assets are available but costly (in order to purchase a contingent asset, households have to pay a xed participation cost) leads to a large increase of wealth inequality. Using a standard calibration our model can match a Gini of 0.93 close to the level of wealth inequality observed in the US. In addition, under this level of participation costs, wealth inequality is particularly sensitive to income inequality. We label this phenomenon as the Inequality Accelerator. We demonstrate how costly access to contingent asset-markets generates these e ects. The key insight stems from the non-monotonic relationship between wealth and desired degree of insurance, in an economy with participation costs. Poor borrowing constrained households remain uninsured, middle-class households are almost perfectly insured, while rich households decide to self-insure by purchasing risk-free assets. This feature of households' risk management has crucial e ects in asset prices, wealth inequality, and social mobility

Credibility and Monetary Policy

This paper revisits the ability of central banks to manage private sector's expectations depending on its credibility and how this affects the use of interest rate rules and pegs to achieve monetary policy objectives. When private agents can only provide limited incentives for the central bank to follow a policy, we show that resulting limited credibility allows a central bank to prevents the inflation from diverging by defaulting on past promises if necessary. As a result, the Taylor rule, when expected, anchors inflation expectations on a unique equilibrium path as long as the Taylor principle is satisfied. Finally, we also show that limited credibility restricts the impact of long-term interest rate pegs, so as to make current conditions less dependent on future policy changes

Endogenous partial insurance and inequality

In this paper, we propose a model of endogenous partial insurance and we investigate its implications for macroeconomic outcomes, such as wealth inequality, asset accumulation, interest rate, and consumption smoothing. To this end, we include participation costs to state-contingent asset markets into an otherwise standard Aiyagari (1994) model. We highlight the resulting nonmonotonic relationship between wealth and insurance-market participation when insurance is costly. Poor households remain uninsured, middle-class households participate in the insurance market, whereas rich households decide to self-insure by only purchasing risk-free assets. After theoretically characterizing the endogenous partial insurance equilibrium, we quantify its effect, emphasizing the roles of a participation channel and an interest rate channel

Southern Europe's institutional decline

The run up to the euro currency initiated a period of capital inflows into southern European countries, i.e., Spain, Portugal, Italy and Greece. We document that those countries, and only them among OECD countries, concomitantly experienced a decline in the quality of their institutions. We confirm the joint pattern of capital in- flows and institutional decline in a large panel of countries. We show theoretically that this joint pattern naturally follows from a “soft budget constraint” syndrome wherein persistently cheap external funding undermines incentives to maintain good institutions –understood here as the degree of government commitment not to support inefficient firms. Low institutional quality ultimately raises the share of inefficient firms, which lowers average productivity and raises productivity dispersion across firms –the typical pattern of productivity in southern Europe over the period under consideration

Essays in international finance and macroeconomics

Cette dissertation se compose de quatre chapitres. Le premier chapitre analyse la soutenabilité de la dette souveraine lorsque le souverain peut compenser ses résidents afin de réduire les possibles effets collatéraux d’un défaut. Il y est montré qu’en l’absence de coûts de réputation, la dette souveraine est soutenable sous la condition que les expositions domestiques ne soient pas observables par le souverain. Le deuxième chapitre étend cette analyse au cas de deux pays où le secteur privé de l’un peut être exposé à la dette souveraine de l’autre. Je montre alors qu’en case de défaut souverain, il peut être optimal de compenser le secteur privé en rachetant la dette souveraine en défaut. Ex ante, il en résulte une garantie implicite sur les dettes souveraines. Le troisième chapitre considère l’interaction entre dette souveraine et politiques fiscales. Il établit que lorsque l’économie domestique est Ricardienne, le gouvernement peut parfaitement compenser ses résidents and, ainsi, il n’y a pas de coûts internes à faire défaut. Il caractérise ensuite les déviations de l’équivalence Ricardienne qui sont à même de soutenir la dette souveraine Le quatrième chapitre, coécrit avec Roberto Pancrazi, étudie l’impact théorique des coûts de participation aux marchés d’assurance sur leur capacité à lisser leur consommation en présence de risques de revenue idiosyncrasiques. Cet impact théorique est ensuite confronté aux données.This dissertation is made of four distinct chapters. In the first chapter, I investigate sovereign debt repayment incentives when countries can implement domestic transfers to mitigate internal costs of default. I show that, in the absence of reputation costs and international sanctions, sovereign repayment emerges as an equilibrium outcome if and only if individual domestic exposures to the domestic debt are not observable by the government. In the second chapter, I extend this mechanism to a two-country situation where one country's private sector is exposed to the second country's sovereign debt. I show that, in case of the second country's default, the optimal compensation can take the form of a purchase of the defaulting bonds. Ex ante, this leads to the existence of an implicit guarantee on sovereign debts. In the third chapter, I consider the connection between sovereign debt repayment incentives and domestic fiscal and redistributive policies. I establish that when the domestic economy is Ricardian, the government can perfectly compensate domestic agents and, thus, no internal cost of default emerges. Then I characterize deviations from Ricardian equivalence that are able to sustain external debt. In the fourth chapter, coauthored with Roberto Pancrazi, we investigate the impact of participation costs to insurance markets on households' ability to smooth consumption. We build a model where households face idiosyncratic risks against which they can purchase insurance, provided that they pay a fixed participation cost. We then confront our results to households' consumption data

Preparación de compuestos PLA-modificado/OMMT a escala laboratorio: comportamiento termo-mecánico

El objetivo de este proyecto era la preparación y la caracterización de diferentes tipos de mezclas de PLA 2002-D con un CE y nanopartículas, con el fin de mejorar las propiedades del PLA. Los tipos de mezclas estudiadas fueron del PLA secado, PLA blanco, PLA + el 1 % CE, y PLA 0,5 % nano. Las mezclas fueron realizadas en un mezclador de escala laboratorio (brabender) y las placas fabricadas con una prensa. Primero los ensayos de infrarrojos, nos permitieron verificar la presencia de todas las funciones químicas en los componentes que íbamos a utilizar. Luego hicimos ensayos de reología con el fin de caracterizar el comportamiento de nuestras mezclas en estado fundido. Estos ensayos permitimos de conocer la viscosidad de nuestros materiales, que será útil en el momento de la extrusión reactiva, así como nos dado una idea de la tasa de ramificación. Efectuamos ensayos de DSC que nos permitió de ver cómo evolucionaba la estabilidad térmica de nuestros mezclas en función de los aditivos del PLA. Esta estabilidad térmica fue caracterizada por la temperatura de transición vítrea, la temperatura de cristalización y la temperatura de fusión. Gracias a estos ensayos pudimos tener también una idea de la tasa de cristalinidad de diferentes mezclas. Los últimos tipos de ensayos fueron los de DMTA que gracias a las curvas de modulo de almacenamiento y de Tan (δ) vinieron para confirmar lo que habíamos deducido anteriormente gracias a las curvas de DSC y de reología sobre la cristalinidad de nuestras mezclas. Después de estos ensayos pudimos poner en contacto la tasa de ramificación con la tasa de cristalinidad en nuestras mezclas. Con el fin de estudiar la competencia o la complementariedad de los efectos de los componentes que habíamos añadido al PLA 2002-D efectuamos los mismos ensayos sobre el PLA +1 %CE +0,5 %nano. En este caso, notamos que el masterbach compensa la degradación inducida por las nanoparticulas.Incomin

Farmer (Sarah), Oradour 10 juin 1944. Arrêt sur mémoire

L’historienne américaine de Berkeley (Californie) Sarah Farmer, spécialiste d’histoire française, nous livre ici une seconde édition revue et augmentée d’un ouvrage de 1994, où elle s’était appuyée sur les interviews des survivants du massacre d’Oradour. Sarah Farmer n’offre pas une analyse des faits eux-mêmes et se contente d’un récit linéaire du déroulement du massacre de 1944 et du procès de 1953 (qui est ici modifié et plus développé que dans la première édition de 1994 parue chez Calmann..

Whole blood assessment of antigen specific cellular immune response by real time quantitative PCR: a versatile monitoring and discovery tool

BACKGROUND: Monitoring of cellular immune responses is indispensable in a number of clinical research areas, including microbiology, virology, oncology and autoimmunity. Purification and culture of peripheral blood mononuclear cells and rapid access to specialized equipment are usually required. We developed a whole blood (WB) technique monitoring antigen specific cellular immune response in vaccinated or naturally sensitized individuals. METHODS: WB (300 microl) was incubated at 37 degrees C with specific antigens, in the form of peptides or commercial vaccines for 5-16 hours. Following RNAlater addition to stabilize RNA, the mixture could be stored over one week at room temperature or at 4 degrees C. Total RNA was then extracted, reverse transcribed and amplified in quantitative real-time PCR (qRT-PCR) assays with primers and probes specific for cytokine and/or chemokine genes. RESULTS: Spiking experiments demonstrated that this technique could detect antigen specific cytokine gene expression from 50 cytotoxic T lymphocytes (CTL) diluted in 300 microl WB. Furthermore, the high sensitivity of this method could be confirmed ex-vivo by the successful detection of CD8+ T cell responses against HCMV, EBV and influenza virus derived HLA-A0201 restricted epitopes, which was significantly correlated with specific multimer staining. Importantly, a highly significant (p = 0.000009) correlation between hepatitis B surface antigen (HBsAg) stimulated IL-2 gene expression, as detectable in WB, and specific antibody titers was observed in donors vaccinated against hepatitis B virus (HBV) between six months and twenty years before the tests. To identify additional markers of potential clinical relevance, expression of chemokine genes was also evaluated. Indeed, HBsAg stimulated expression of MIP-1beta (CCL4) gene was highly significantly (p = 0.0006) correlated with specific antibody titers. Moreover, a longitudinal study on response to influenza vaccine demonstrated a significant increase of antigen specific IFN-gamma gene expression two weeks after immunization, declining thereafter, whereas increased IL-2 gene expression was still detectable four months after vaccination. CONCLUSION: This method, easily amenable to automation, might qualify as technology of choice for high throughput screening of immune responses to large panels of antigens from cohorts of donors. Although analysis of cytokine gene expression requires adequate laboratory infrastructure, initial antigen stimulation and storage of test probes can be performed with minimal equipment and time requirements. This might prove important in "field" studies with difficult access to laboratory facilities

In Vitro Modeling of Tumor-Immune System Interaction.

Immunotherapy has emerged during the past two decades as an innovative and successful form of cancer treatment. However, frequently, mechanisms of actions are still unclear, predictive markers are insufficiently characterized, and preclinical assays for innovative treatments are poorly reliable. In this context, the analysis of tumor/immune system interaction plays key roles, but may be unreliably mirrored by in vivo experimental models and standard bidimensional culture systems. Tridimensional cultures of tumor cells have been developed to bridge the gap between in vitro and in vivo systems. Interestingly, defined aspects of the interaction of cells from adaptive and innate immune systems and tumor cells may also be mirrored by 3D cultures. Here we review in vitro models of cancer/immune cell interaction and we propose that updated technologies might help develop innovative treatments, identify biologicals of potential clinical relevance, and select patients eligible for immunotherapy treatments