On the Multivariate Upcrossings Index

The multivariate extremal index function is a measure of the clustering among the extreme values of a multivariate stationary sequence. In this article, we introduce a measure of the degree of clustering of upcrossings in a multivariate stationary sequence, called multivariate upcrossings index, which is a multivariate generalization of the concept of upcrossings index. We derive the main properties of this function, namely the relations with the multivariate extremal index and the clustering of upcrossings.

Imposing general local and asymptotic dependence restrictions on the sequence or on its marginals we compute the multivariate upcrossings index from the marginal upcrossings indices and from the joint distribution of a finite number of variables. A couple of illustrative examples are exploited.     

The influence of the sample on the posterior distribution

In this paper, we present conditions on the likelihood function and on the prior distribution which permit us to assess the effect of the sample on the posterior distribution. Our work is inspired by Whitt (1979) J. Amer. Statist. Assoc. 74, and is based on the notions of multivariate totally positive and (strongly) mul-tivariate reverse rule functions introduced and studied by Karlin and Rinott (1980a, b)     

Using remote sensing and census tract data to improve representation of population spatial distribution: case studies in the Brazilian Amazon

This work proposes a methodological approach to redistribute population data obtained from polygonal census tracts into population density surfaces (grids) based on a cell space database. The methodology was first developed for the municipality of Marabá, Pará state, in the Brazilian Amazon. We used a dasymetric method to eliminate areas of environmental restriction to human presence; then integrated environmental data indicative of human presence to generate a potential surface of population occurrence; and finally, census population count data were redistributed into cells. The methodology was subsequently adapted for 13 municipalities of the Sustainable Forests District (SFD) of BR-163, generating population distribution surfaces for 2000 and 2007. The evolution of the resident population over the SFD-BR163 showed spatial patterns compatible with the occupation process described in the literature and verified by fieldwork. To be applied over other areas, the proposed methodology must be adapted with local parameters but in this way, population density surfaces can be useful as an additional data source to study population and environment relationships.     

Measuring and understanding trade in service tasks

The revolution in information and communications technologies has put service tasks with strong tradability characteristics at high risk of being offshored. This article reviews studies proposing indicators of service tradability, exploring the labour market implications of service offshoring and developing theories to rationalize the facts. It suggests that both skill intensity and tradability are determinants of wage and employment effects. Nonetheless, the lack of widely accepted definitions of tradability, the absence of high‐quality data on service trade flows and the difficulty of measuring import competition at higher disaggregation levels pose difficulties in achieving further progress, pointing to areas for future research.     

Correction to: Comparison of joint control schemes for multivariate normal i.i.d. output

AStA Advances in Statistical Analysis - In the original paper, we incorrectly stated that...     

Unveiling Research Trends for Organizational Reputation in the Nonprofit Sector

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Public scrutiny and the need for funds in a more competitive environment are pressuring nonprofits to be more consciously...     

Between two Beneditos: enslaved wet-nurses amid slavery’s decline in southeast Brazil

ABSTRACT

This article discusses a series of questions related to the presence of enslaved women, female slaves working toward contractual or bequeathed freedom, and freedwomen in the domestic sphere in the final years of slavery in Brazil, with an initial emphasis on the contradictions between medical and sanitarian discourses that promoted a new, bourgeois vision of the home and the continued existence of the master-slave relationship and tutelary relations derived therefrom in the most intimate spaces of wealthy households in the cities and towns of the country’s coffee-growing southeast. The article also seeks to reconstruct the perspective of these captive and servant-class women at the moment of slavery’s extinction, thus providing a new perspective on the latter process by noting how the abolition of slavery was conditioned by the gendering of household work. A reconstruction of the life of Ambrosina, a slave woman rented out by her owner to serve another family as a wet nurse, then accused of murder after the death of her young charge, is the means by which these contributions are made.     

I’m not like everybody else: urbanization factors shaping spatial distribution of native and invasive ants are species-specific

Urbanization is a major global change inducing complex and multiple modifications of landscapes and ecosystems. The spatial distributions of organisms experiencing these modifications will likely shift specifically, depending on each species’ response to each environmental modification induced by urbanization. We sampled two ant genera (Lasius and Tetramorium) at 1248 locations along an urbanization gradient in Lyon, France and used high resolution spatial layers for 18 spatial (e.g., open habitat fragmentation, bioclimatic data and surface temperatures) and temporal (e.g., comparison of Normalized Difference Vegetation Index between 1986 and 2015) environmental variables associated with urbanization. Coupling two different analytical methods (Outlying Mean Index and Boosted Regression Trees), we showed that each species’ distribution was influenced by its own combination of environmental factors. Two morphologically cryptic Tetramorium species (T. sp.E and T. sp.U2) were both highly abundant but with opposite responses to urbanization: while T. sp.E was favored by urbanized habitat, T. sp.U2 avoided urbanized areas. Among Lasius species, we detected 63 occurrences of the invasive ant Lasius neglectus, the distribution of which was favored only by embankments along roads. We found that, even at this reduced spatial scale, climatic effects influenced most species and interacted with urbanization factors.     

Bootstrap Bartlett correction in inflated beta regression

The inflated beta regression model aims to enable the modeling of responses in the intervals (0, 1], [0, 1), or [0, 1]. In this model, hypothesis testing is often performed based on the likelihood ratio statistic. The critical values are obtained from asymptotic approximations, which may lead to distortions of size in small samples. In this sense, this article proposes the bootstrap Bartlett correction to the statistic of likelihood ratio in the inflated beta regression model. The proposed adjustment only requires a simple Monte Carlo simulation. Through extensive Monte Carlo simulations the finite sample performance (size and power) of the proposed corrected test is compared to the usual likelihood ratio test and the Skovgaard adjustment already proposed in the literature. The numerical results evidence that inference based on the proposed correction is much more reliable than that based on the usual likelihood ratio statistics and the Skovgaard adjustment. At the end of the work, an application to real data is also presented.