The random robin problem for laplace's equation

A random generalized solution to the Robin problem for Laplace's equation is defined in terms of the sections of the random boundary data. Existence, uniqueness, and properties are established for such a solution. Particularizations to the Dirichlet and Newmann problems as well as generalization to the Robin-Poisson problem are mentioned. Applications of the results are provided.     

Repeated electoral competition over nonlinear income tax schedules

We consider a repeated electoral competition game between two parties, each representing a constituent with a given income level. Parties are unable to commit to a policy before the election; they choose a nonlinear income tax schedule once elected. In each period, citizens cast a vote either for the incumbent or for the challenger. We first show that there exist (pure strategy) subgame perfect equilibria where both parties choose the most-preferred tax schedule of their constituent, subject to the constraint that they are reelected. We characterize a specific class of these BPR (Best Policy with Reelection) equilibria in which one of the parties plays its constituent’s unconstrained optimal tax function. Equilibrium tax schedules are always piecewise linear. Depending on the income levels of the two parties’ constituents, we obtain either classical left-vs-right equilibria (where the poor vote for one party and the rich for the other one) or ends-against-the-middle equilibria (where both poor and rich vote for one party while the middle class votes for the other party). In both types of equilibria, both parties propose the same tax schedule to a subset of the population.     

Polygyny, Partnership Concurrency, and HIV Transmission in Sub-Saharan Africa

We study the relationship between polygyny and HIV infection using nationally representative survey data with linked serostatus information from 20 African countries. Our results indicate that junior wives in polygynous unions are more likely to be HIV positive than spouses of monogamous men, but also that HIV prevalence is lower in populations with more polygyny. With these results in mind, we investigate four explanations for the contrasting individual- and ecological-level associations. These relate to (1) the adverse selection of HIV-positive women into polygynous unions, (2) the sexual network structure characteristic of polygyny, (3) the relatively low coital frequency in conjugal dyads of polygynous marriages (coital dilution), and (4) the restricted access to sexual partners for younger men in populations where polygynous men presumably monopolize the women in their community (monopolizing polygynists). We find evidence for some of these mechanisms, and together they support the proposition that polygynous marriage systems impede the spread of HIV. We relate these results to the debate about partnership concurrency as a primary behavioral driver for the fast propagation of HIV in some parts of sub-Saharan Africa.     

NUSAP Method for Evaluating the Data Quality in a Quantitative Microbial Risk Assessment Model for Salmonella in the Pork Production Chain

The numeral unit spread assessment pedigree (NUSAP) system was implemented to evaluate the quality of input parameters in a quantitative microbial risk assessment (QMRA) model for Salmonella spp. in minced pork meat. The input parameters were grouped according to four successive exposure pathways: (1) primary production (2) transport, holding, and slaughterhouse, (3) postprocessing, distribution, and storage, and (4) preparation and consumption. An inventory of 101 potential input parameters was used for building the QMRA model. The characteristics of each parameter were defined using a standardized procedure to assess (1) the source of information, (2) the sampling methodology and sample size, and (3) the distributional properties of the estimate. Each parameter was scored by a panel of experts using a pedigree matrix containing four criteria (proxy, empirical basis, method, and validation) to assess the quality, and this was graphically represented by means of kite diagrams. The parameters obtained significantly lower scores for the validation criterion as compared with the other criteria. Overall strengths of parameters related to the primary production module were significantly stronger compared to the other modules (the transport, holding, and slaughterhouse module, the processing, distribution, and storage module, and the preparation and consumption module). The pedigree assessment contributed to select 20 parameters, which were subsequently introduced in the QMRA model. The NUSAP methodology and kite diagrams are objective tools to discuss and visualize the quality of the parameters in a structured way. These two tools can be used in the selection procedure of input parameters for a QMRA, and can lead to a more transparent quality assurance in the QMRA.     

The historical calendar as a method of estimating age: The experience of the Moroccan multi-purpose sample survey of 1961-63

Abstract In censuses and surveys in most African countries it has become the practice to estimate informants' age by the method of the historical calendar. This involves an attempt to relate a remembered historical event, occurring during the subject's childhood, with his age at the time. This paper attempts a first evaluation of the method with particular reference to the 1961-63 multi-round survey in rural Morocco. It is shown that in practice the method is highly complex and easily misunderstood by interviewers and respondents. An attempt to lay down a precise procedure by means of a very detailed questionnaire appeared to yield at best only marginally more accurate results than the simpler procedure used in an earlier round. The more complex questionnaire did, however, introduce new patterns of misuse by the interviewer. There was evidence that the historical calendar gave somewhat better data than eye estimates, but results were highly defective for both methods. It is clear that the method is far from perfect. Interviewer training and supervision remain the key to accurate age determination. If the potential benefits of the complex historical calendar method are to be realized, training and supervision need to be even more thorough than where simpler methods are used.     

The costs of immigration to taxpayers: Toward a uniform accounting framework

Large scale immigration to the United States and a sluggish national economy have brought to the forefront of the current immigration policy debate, the question of whether immigrants fully pay—in the form of taxes—for the public services they use. Recent estimates of the costs of immigration differ so widely that they have confused rather than enlightened that debate. This paper argues that a uniform accounting framework must be agreed to if future studies are to provide credible and reliable estimates of costs and benefits upon which immigration policy can be formulated. The key conceptual, factual, and accounting issues that are to be addressed for the development of such a framework are outlined.     

The relationship between migration and fertility in an historical context: the case of Morocco in the 1960s

The relationship between migration and fertility was explored on the basis of data collected in a 1966 survey conducted in the 9 largest cities of Morocco. Existing contradictory findings suggest the need to specify and analyze the conditions under which fertility differentials by migration status are observed. The 2 theoretically most interesting conditions were considered: the historical context of migration; and the type of migration. A stratified area probability sample was selected with different sampling fractions within each city and city-strata. In each sampled household, 1 married woman under age 50 and 1 50 years and over, as well as single women ranging in age from 15-24, were selected at random and interviewed by female interviewers. The present analysis was limited to data for ever married women under age 50. The following variables were used as controls in the analysis of the relationship between migration status and fertility: the intermediate variable of age at marriage; measures of socioeconomic status; labor force participation of women; and measures of exposure to the modernizing influence of the city. If the 2 conditions of historical context and migration typology had been ignored in the analysis of data for Morocco's cities in 1966, meaningful fertility differentials would not have been evident. It was only after migration typology and historical context were considered that a more noticeable pattern of differential fertility emerged. Migrants of rural or urban origin who moved to the largest cities of Morocco after independence in 1956 had the lowest fertility of any group. The highest fertility was observed for women who moved to these cities before 1956. The fertility of urban natives and of urban migrants who moved before 1956 was between the 2 extreme levels. Controlling for the effects of age at marriage and various socioeconomic factors reduced the fertility differentials but failed to change their pattern. It was hypothesized that the lower fertility of recent migrants may be explained by social mobility.     

Does insurance fraud in automobile theft insurance fluctuate with the business cycle?

Financial institutions face various cyclical risks, but very few studies have analyzed the cyclicality of operational risk. External fraud is an important operational risk faced by insurers. In this research, we analyze the empirical relationship between insurance fraud and the business cycle and we concentrate our study on two insurance contracts that may create an incentive to defraud. We find that residual insurance fraud exists both in the contract with replacement cost endorsement and the contract with no-deductible endorsement in the Taiwan automobile theft insurance market. These results are consistent with previous literature on the relationship between fraud activity and non-optimal insurance contracting. We also show that the severity of insurance fraud is countercyclical. Fraud is stimulated during periods of recession and mitigated during periods of expansion. Although this last result seems intuitive, our contribution is the first to measure its significance.