MICROFINANCE INSTITUTIONS UNDER INTEREST RATES CEILINGS

Microfinance institutions (MFIs) have grown fast in WAEMU surprising political decision makers. They reacted by setting up in the late 90's, a specific legislation. A legal usury rate for credits was defined fixing the borrower ceiling interest rate at 27 percent per year for microfinance institutions and 18 percent for banks. This statutory frame, fast elaborated, revealed early its incapacities and therefore, weakened structures in charge of the regulation of the sector. This structure is confronted with the difficult choice to maintain institutions outside the statutory frame or to apply a rigorous supervision and to precipitate a massive decline of MFIs. This law limits incentives to better governance, the efficiency and the flexibility expected from a good statutory frame. This paper models the behaviour of microfinance institutions in the context of interest rate ceilings and requirement of a minimal level of governance. We use comparative statics to show that a relaxation of the constraint on the usury rate does not lead necessarily to an increase of the borrower interest rate.regulation, usury ; governance ; microfinance

A Semi-parametric Two-component “Compound” Mixture Model and Its Application to Estimating Malaria Attributable Fractions

Malaria remains a major epidemiological problem in many developing countries. Malaria is dened as the presence of parasites and symptoms (usually fever) due to the parasites. In endemic areas, an individual may have symptoms attributable either to malaria or to other causes. From a clinical point of view, it is important to correctly diagnose an individual who has developed symptoms so that the appropriate treatments can be given. From an epidemiologic and economic point of view, it is important to determine the proportion of malaria affected cases in individuals who have symptoms so that policies on intervention programmes can be developed. Once symptoms have developed in an individual, the diagnosis of malaria can be based on analysis of the parasite levels in blood samples. However, even a blood test is not conclusive as in endemic areas, many healthy individuals can have parasites in their blood slides. Therefore, data from this type of studies can be viewed as coming from a mixture distribution, with the components corresponding to malaria and nonmalaria cases. A unique feature in this type of data, however, is the fact that a proportion of the non-malaria cases have zero parasite levels. Therefore, one of the component distribu-tions is itself a mixture distribution. In this article, we propose a semi-parametric likelihood approach for estimating the proportion of clinical malaria using parasite level data from a group of individuals with symptoms. Our approach assumes the density ratio for the parasite levels in clinical malaria and non-clinical malaria cases can be modeled using a logistic model. We use empirical likelihood to combine the zero and non-zero data. The maximum semi-parametric likelihood estimate is more ecient than existing non-parametric estimates using only the frequencies of zero and non-zero data. On the other hand, it is more robust than a fully parametric maximum likelihood estimate that assumes a parametric model for the non-zero data. Simulation results show that the performance of the proposed method is satisfactory. The proposed method is used to analyze data from a malaria survey carried out in Tanzania.Attributable fraction; Density ratio model; Empirical likelihood; Malaria; Mixture methods.

Persistence of coherent quantum dynamics at strong dissipation

The quantum dynamics of a two state system coupled to a bosonic reservoir with sub-Ohmic spectral density is investigated for strong friction. Numerically exact path integral Monte Carlo methods reveal that in contrast to conventional expectations, coherent dynamics never turns into incoherent decay for a broad class of spectral distributions. Coherences associated with substantial system-reservoir entanglement exist in non-equilibrium even when strong dissipation makes the thermodynamic state of the system to behave essentially classical. This may be of relevance for current experiments with nanoscale devices and bio-molecular aggregates.Comment: 5 pages, 5 figure

Emergent hyperuniformity in periodically-driven emulsions

We report the emergence of large-scale hyperuniformity in microfluidic emulsions. Upon periodic driving confined emulsions undergo a first-order transition from a reversible to an irreversible dynamics. We evidence that this dynamical transition is accompanied by structural changes at all scales yielding macroscopic yet finite hyperuniform structures. Numerical simulations are performed to single out the very ingredients responsible for the suppression of density fluctuations. We show that as opposed to equilibrium systems the long-range nature of the hydrodynamic interactions are not required for the formation of hyperuniform patterns, thereby suggesting a robust relation between reversibility and hyperuniformity which should hold in a broad class of periodically driven materials.Comment: 5p, 3f, submitte