Properties and applications of the Poisson-reciprocal inverse Gaussian distribution

The barely known continuous reciprocal inverse Gaussian distribution is used in this paper to introduce the Poisson-reciprocal inverse Gaussian discrete distribution. Several of its most relevant statistical properties are examined, some of them directly inherited from the reciprocal of the inverse Gaussian distribution. Furthermore, a mixed Poisson regression model that uses the reciprocal inverse Gaussian as mixing distribution is presented. Parameters estimation in this regression model is performed via an EM type algorithm. In light of the numerical results displayed in the paper, the distributions introduced in this work are competitive with the classical negative binomial and Poisson-inverse Gaussian distributions.     

Are the closed landfills recovered habitats for small rodents? A case study in a riparian site,Buenos Aires,Argentina

The establishment of landfills in urban areas leads to extensive disturbances. Their development after landfill closure depends on the characteristics of the soil cover, the surrounding communities and the dispersal of plants and animals. This study was carried out in a landfill closed in 2004, surrounded by an urban area, freshwater marshes and a riparian forest. The aim of this study was to determine the role that the closed landfill may play in maintaining rodent communities typical of this zone and its relation to characteristics of the sites. Four rodent and plant samplings were carried out from December 2005 to September 2006 at five sites inside the landfill: three filled cells and two areas of the riparian margin. We recorded a total of 433 individual rodents. The rodent community of the closed landfill included species typical of rural, riparian and rural habitats: Akodon azarae (358), Oligoryzomys flavescens (32), Deltamys kempi (14), Rattus rattus (14), Cavia aperea (11) and Scapteromys aquaticus (4). Rodent species composition varied among sites, but A. azarae was usually the dominant species. We found a rich rodent community mostly composed of wild species. The relictual riparian margin may have served as a major refuge for native rodent community while the landfill was in operation, and after closure it possibly acted as a source for some species to colonize the covered cells.     

A cost valuation model based on a stochastic representation of the IPAT equation

Within the framework of models for human-driven environmental impact based on the IPAT equation, we develop a model for the evolution of impact (expressed in terms of carbon dioxide emissions) and for the valuation of the economic cost associated to its reduction. We use a stochastic representation of the IPAT equation that is alternative to the STIRPAT model. This first step leads to a stochastic differential equations model that describes trends in carbon dioxide emissions on the basis of economic and demographic dynamics. As an example, we estimate the model parameters for the United States. We then use this framework to build a model for the assessment of the economic costs related to a reduction of carbon dioxide emissions for a country committed to respect an international agreement, such as the Kyoto protocol. In particular, we show that the adherence to an environmental treaty may be traced back to a problem of cost valuation and to a decision under risk. This allows us to use the mathematical tools that have been developed in quantitative finance, in the context of option pricing, to determine the expected investment that is required to reduce the emissions of a country by a certain amount and within a well-defined temporal frame.

The relationship between Civil Unions and fertility in France: Preliminary evidence

This paper explores the relationship between fertility and the introduction of new laws regulating cohabitation, in a context of low fertility and high out of wedlock childbearing. We show that in France, while fertility and marriage rates moved closely together before 1999, since the introduction (in 1999) of the “Pacte Civil de Solidarité” (PACS)—a cohabitation contract less binding than marriage—this relationship is much weaker. Surprisingly, legal unions (defined as marriage plus PACS) and fertility continue to move together after this date. We provide evidence of the relationship between the introduction of PACS and fertility, utilizing the regional variation in the number of PACS per woman (PACS intensity) and the differences in fertility before and after 1999. We show that French Departments with high PACS intensity did not show a different trend in fertility before 1999 than those with low PACS intensity (excluding Metropolitan Paris). However, they did experience an increase in their fertility levels after the introduction of PACS. This suggests the need to collect better and more detailed data, in order to assess whether the recent increases in French fertility can be partially explained by the availability of PACS.     

Promises and Pitfalls of Using Digital Traces for Demographic Research

The digital traces that we leave online are increasingly fruitful sources of data for social scientists, including those interested in demographic research. The collection and use of digital data also presents numerous statistical, computational, and ethical challenges, motivating the development of new research approaches to address these burgeoning issues. In this article, we argue that researchers with formal training in demography—those who have a history of developing innovative approaches to using challenging data—are well positioned to contribute to this area of work. We discuss the benefits and challenges of using digital trace data for social and demographic research, and we review examples of current demographic literature that creatively use digital trace data to study processes related to fertility, mortality, and migration. Focusing on Facebook data for advertisers—a novel “digital census” that has largely been untapped by demographers—we provide illustrative and empirical examples of how demographic researchers can manage issues such as bias and representation when using digital trace data. We conclude by offering our perspective on the road ahead regarding demography and its role in the data revolution.     

Fast and exact simulation of Gaussian random fields defined on the sphere cross time

Statistics and Computing - We provide a method for fast and exact simulation of Gaussian random fields on the sphere having isotropic covariance functions. The method proposed is then extended to...