490 research outputs found
Essays in banking
This thesis consists of three essays on household finance and banking. The first chapter, co-authored with Alberto Polo and Quynh-Anh Vo from the bank of England, examines the role of menus of contracts in the UK mortgage market. Using data from the UK mortgage market and a structural model of screening with endogenous menus, I quantify the impact of asymmetric information on equilibrium contracts and welfare. I show that when lenders screen borrowers using a menu, they generate a contractual externality by making the composition of their competitors’ borrowers worse. Counterfactual simulations of a social planner problem show that, because of the externality, there is too much screening along the loan-to-value dimension. The deadweight loss, expressed in borrower utility, is equivalent to an interest rate increase of 30-60 basis points (a 15-30 percent increase) on all loans. The second chapter theoretically analyses the interaction between competition and adverse selection in markets where menus are used. Using a discrete choice approach to model competition, I characterise the unique pure strategy Nash equilibrium in a contract theory model with adverse selection and imperfect competition. I highlight a novel contractual externality leading to a welfare trade-off between competition and adverse selection. Lowering competition lowers concerns of losing market shares; this can improve welfare by giving lenders more flexibility on how to use contract terms and prices to sort borrowers efficiently. It also lowers lenders’ incentives to implement socially inefficient strategies that rely on taking advantage of their competitors’ menus to attract only low-cost borrowers (cream-skimming). However, low competition also allows lenders to apply high mark-ups, reducing borrowers’ utility. When the externality is high, lowering competition leads to a Pareto improvement. The third chapter theoretically studies the impact of designing lender-specific capital regulation regimes. To that end, I build a novel model of banking in which setting individualized capital requirements allows to better deal with each lender’s excessive lending behaviour. However, creating different capital requirements also increases lenders’ fixed cost of understanding and interpreting the regulation. Changes in the fixed cost endogenously affect the market structure and bank interest rate markups. Those changes feed back into lenders’ incentives to over-lend. Due to this general equilibrium effect, I show that increasing capital requirement heterogeneity can increase the friction it was designed to reduce. Motivated by this theoretical result, I develop a sufficient statistic approach to empirically assess the impact of capital requirement complexity on welfare
Promoteurs immobiliers privés et problématiques de développement durable urbain
At the turn of the century, as the great housing issues – finding homes, building, living differently, reusing thealready built, dealing with crises and constraints – are becoming more acute, new problems have emerged, under thebroader question of sustainable development, and thus questioning the way cities are organised. Therefore, privatereal estate developers are approached over this question, which has become urgent in the wake of the 2007 GrenelleEnvironment conference. From then on, faced with the issues of sustainable development, private contributors tourban construction need to take several scales into account at the same time – housing lot, building, neighbourhood,city – in order to address the many components of sustainability. Private developers first dealt with buildings’energetic treatments and outer structure, but are gradually considering whole sustainable neighbourhoods andcities. This study has focused on fieldwork in two areas : the Ginko eco-neighbourhood in Bordeaux and theconverted Macdonald warehouse. These have enabled us to analyze an understudied area of reasearch, i.e. privatefunding of sustainable neighbourhoods. The birth of sustainable urbanism gives a second life to those two places.It is also an opportunity for private developers to work both in terms of sustainable development, and on the scaleof entire neighbourhoods. This dual aspect, resulting from interests common to public and private actors, enablesreal estate developers to take a truly active part in the rise of sustainable neighbourhoods.Alors même que les grandes priorités de la question du logement (loger, construire et habiter différemment, habiterl’existant, crises et contraintes) tendent à converger et à s’agréger à la charnière du changement de siècle, de nouvellesproblématiques, regroupées sous celle plus globale du développement durable, émergent et (ré)interrogent la productionde la ville. Les promoteurs immobiliers privés sont alors interpellés et mobilisés afin de répondre à cette nouvelleproblématique qui devient même prescription à la suite du Grenelle de l’environnement (2007). Les problématiquesde la durabilité proposent dès lors aux acteurs privés de la fabrique urbaine de se projeter sur une ligne de déclinaisonlogement-bâtiment-quartier-ville et à y opérer des allers-retours afin de répondre à la transversalité des composantes dela durabilité. D’un premier temps consacré au traitement énergétique du bâtiment et de son enveloppe, des promoteursse positionnent peu à peu à l’échelle du quartier durable et de la ville durable. Deux terrains d’études, l’écoquartierbordelais Ginko et la reconversion de l’entrepôt Macdonald, proposent d’éclaircir un pan encore peu approprié parla bibliographie : le portage privé d’opérations de quartiers durables. L’éclosion de l’urbanisme durable ouvre unedeuxième vie à ces deux opérations. Elle ouvre également de nouvelles opportunités aux acteurs privés pouvant opérerun balancement entre les échelles de la durabilité et en mesure de se projeter à l’échelle du quartier. Ce point derencontre, établi par une convergence d’intérêts communs entre acteurs publics et privés, permet alors aux promoteursaménageursde se poser comme force de proposition dans l’édification de quartiers durables
A Natural Steganography Embedding Scheme Dedicated to Color Sensors in the JPEG Domain
International audienceUsing Natural Steganography (NS), a cover raw image acquired at sensitivity ISO 1 is transformed into a stego image whose statistical distribution is similar to a cover image acquired at sensitivity ISO 2 > ISO 1. This paper proposes such an embedding scheme for color sensors in the JPEG domain, extending thus the prior art proposed for the pixel domain and the JPEG domain for monochrome sensors. We first show that color sensors generate strong intra-block and inter-block dependencies between DCT coefficients and that theses dependencies are due to the demosaicking step in the development process. Capturing theses dependencies using an empirical covariance matrix, we propose a pseudo-embedding algorithm on greyscale JPEG images which uses up to four sub-lattices and 64 lattices to embed information while preserving the estimated correlations among DCT coefficients. We then compute an approximation of the average embedding rate w.r.t. the JPEG quality factor and evaluate the empirical security of the proposed scheme for linear and non-linear demosaicing schemes. Our experiments show that we can achieve high capacity (around 2 bit per nzAC) with a high empirical security (P E 30% using DCTR at QF 95)
JPEG Steganography and Synchronization of DCT Coefficients for a Given Development Pipeline
This short paper proposes to use the statistical analysis of the correlation
between DCT coefficients to design a new synchronization strategy that can be
used for cost-based steganographic schemes in the JPEG domain. First, an
analysis is performed on the covariance matrix of DCT coefficients of
neighboring blocks after a development similar to the one used to generate
BossBase. This analysis exhibits groups of uncorrelated coefficients: 4 groups
per block and 2 groups of uncorrelated diagonal neighbors together with groups
of mutually correlated coefficients groups of 6 coefficients per blocs and 8
coefficients between 2 adjacent blocks. Using the uncorrelated groups, an
embedding scheme can be designed using only 8 disjoint lattices. The cost map
for each lattice is updated firstly by using an implicit underlying Gaussian
distribution with a variance directly computed from the embedding costs, and
secondly by deriving conditional distributions from multivariate distributions.
The covariance matrix of these distributions takes into account both the
correlations exhibited by the analysis of the covariance matrix and the
variance derived from the cost. This synchronization scheme enables to obtain a
gain of PE of 5% at QF 95 for an embedding rate close to 0.3 bnzac coefficient
using DCTR feature sets
Typologie et représentations des ensembles résidentiels fermés ou sécurisés en France
Cette contribution vise dans un premier temps à réaliser un recensement des programmes fermés avec contrôle des accès en France. Puis, une typologie des ensembles fermés a été mise en œuvre. Enfin, l'article s'oriente vers une étude des représentations qui ont cours à propos des ensembles résidentiels fermés, par une analyse des discours produits par les principaux acteurs concernés par le phénomène : les promoteurs, les résidants de ces complexes fermés et enfin les élus et techniciens en charge de l'urbanisme ou de l'habitat
Biases on the cosmological parameters and thermal SZ residuals
We examine the biases induced on cosmological parameters when the presence of
secondary anisotropies is not taken into account in Cosmic Microwave Background
analyses. We first develop an exact analytical expression for computing the
biases on parameters when any additive signal is neglected in the analysis. We
then apply it in the context of the forthcoming Planck experiment. For
illustration, we investigate the effect of the sole residual thermal
Sunyaev--Zel'dovich signal that remains after cluster extraction. We find in
particular that analyses neglecting the presence of this contribution introduce
on the cosmological parameters n_s and tau biases, at least 6.5 and 2.9 times
their one sigma confidence intervals. The Omega_b parameter is also biased to a
lesser extent.Comment: 7 pages, 5 figures, published in MNRA
The ISW-tSZ cross correlation: ISW extraction out of pure CMB data
If Dark Energy introduces an acceleration in the universal expansion then
large scale gravitational potential wells should be shrinking, causing a
blueshift in the CMB photons that cross such structures (Integrated Sachs-Wolfe
effect, [ISW]). Galaxy clusters are known to probe those potential wells. In
these objects, CMB photons also experience inverse Compton scattering off the
hot electrons of the intra-cluster medium, and this results in a distortion
with a characteristic spectral signature of the CMB spectrum (the so-called
thermal Sunyaev-Zel'dovich effect, [tSZ]). Since both the ISW and the tSZ
effects take place in the same potential wells, they must be spatially
correlated. We present how this cross ISW-tSZ signal can be detected in a
CMB-data contained way by using the frequency dependence of the tSZ effect in
multi frequency CMB experiments like {\it Planck}, {\em without} requiring the
use of external large scale structure tracers data. We find that by masking low
redshift clusters, the shot noise level decreases significantly, boosting the
signal to noise ratio of the ISW--tSZ cross correlation. We also find that
galactic and extragalactic dust residuals must be kept at or below the level of
~0.04 muK^2 at l=10, a limit that is a factor of a few below {\it Planck}'s
expectations for foreground subtraction. If this is achieved, CMB observations
of the ISW-tSZ cross correlation should also provide an independent probe for
the existence of Dark Energy and the amplitude of density perturbations.Comment: submitted to MNRA
Ebola Virus Infection: a review on the pharmacokinetic and pharmacodynamic properties of drugs considered for testing in human efficacy trials
International audienceThe 2014-2015 outbreak of Ebola virus disease (EVD) is the largest epidemic to date in terms of number of cases, of death and affected areas. In October 2015, no antiviral agents had proven an antiviral efficacy in patients. However in September 2014 WHO inventoried and regularly updated since then a list of potential drug candidates with demonstrated antiviral efficacy in vitro or in animal models. This includes agents belonging to various therapeutic classes, namely direct antiviral agents (favipiravir and BCX4430), combination of antibodies (ZMapp), type I interferons, RNA interference-based drugs (TKM-Ebola and AVI-7537) and anticoagulant drug (rNAPc2).Here, we review the pharmacokinetic and pharmacodynamic information that are presently available on these drugs, using data obtained in healthy volunteers for pharmacokinetics and data obtained in human clinical trials or animal models for pharmacodynamics. Future studies evaluating these drugs in clinical trials will be critical to confirm their efficacy in humans, propose appropriate doses and evaluate the possibility of treatment combinations
CMB and SZ effect separation with Constrained Internal Linear Combinations
The `Internal Linear Combination' (ILC) component separation method has been
extensively used on the data of the WMAP space mission, to extract a single
component, the CMB, from the WMAP multifrequency data. We extend the ILC
approach for reconstructing millimeter astrophysical emissions beyond the CMB
alone. In particular, we construct a Constrained ILC to extract clean maps of
both the CMB or the thermal Sunyaev Zeldovich (SZ) effect, with vanishing
contamination from the other. The performance of the Constrained ILC is tested
on simulations of Planck mission observations, for which we successfully
reconstruct independent estimates of the CMB and of the thermal SZ.Comment: 7 pages, 3 figures, submitted to MNRA
Stéganographie naturelle pour images JPEG
International audienc
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