An automatic classification and robust segmentation procedure of spatial objects

This paper proposes a statistical procedure for the automatic volumetric primitives classification and segmentation of 3D objects surveyed with high density laser scanning range measurements. The procedure is carried out in three main phases: first, a Taylor’s expansion nonparametric model is applied to study the differential local properties of the surface so to classify and identify homogeneous point clusters. Classification is based on the study of the surface Gaussian and mean curvature, computed for each point from estimated differential parameters of the Taylor’s formula extended to second order terms. The geometrical primitives are classified into the following basic types: elliptic, hyperbolic, parabolic and planar. The last phase corresponds to a parametric regression applied to perform a robust segmentation of the various primitives. A Simultaneous AutoRegressive model is applied to define the trend surface for each geometric feature, and a Forward Search procedure puts in evidence outliers or clusters of non stationary data. An erratum to this article can be found at     

How to cut a pizza fairly: Fair division with decreasing marginal evaluations

Existential and constructive solutions to the classic problems of fair division are known for individuals with constant marginal evaluations. By considering nonatomic concave capacities instead of nonatomic probability measures, we extend some of these results to the case of individuals with decreasing marginal evaluations. Received: 12 June 2001/Accepted: 23 May 2002 An earlier version of this paper, Caltech Social Science Working Paper # 1126, was titled “How to cut a cake healthily”. We wish to thank Maristella Botticini, Erio Castagnoli, Marco Dall'Aglio, Paolo Ghirardato, Luigi Montrucchio, Marco Scarsini, Marciano Siniscalchi, as well as Maurice Salles (the Editor), an Associate Editor, and four anonymous Referees for helpful suggestions. The financial support of MIUR, CNR, and Università Bocconi is gratefully acknowledged. Part of this research was done while the first author was visiting Boston University and the California Institute of Technology, which he thanks for their hospitality.     

Minimum Distance Estimation of Search Costs Using Price Distribution

ABSTRACT

It has been shown that equilibrium restrictions in a search model can be used to identify quantiles of the search cost distribution from observedprices alone. These quantiles can be difficult to estimate in practice. This article uses a minimum distance approach to estimate them that is easy to compute. A version of our estimator is a solution to a nonlinear least-square problem that can be straightforwardly programmed on softwares such as STATA. We show our estimator is consistent and has an asymptotic normal distribution. Its distribution can be consistently estimated by a bootstrap. Our estimator can be used to estimate the cost distribution nonparametrically on a larger support when prices from heterogenous markets are available. We propose a two-step sieve estimator for that case. The first step estimates quantiles from each market. They are used in the second step as generated variables to perform nonparametric sieve estimation. We derive the uniform rate of convergence of the sieve estimator that can be used to quantify the errors incurred from interpolating data across markets. To illustrate we use online bookmaking odds for English football leagues’ matches (as prices) and find evidence that suggests search costs for consumers have fallen following a change in the British law that allows gambling operators to advertise more widely. Supplementary materials for this article are available online.     

Swinger economics

Swinging is a sexual behaviour of increasing relevance but substantially ignored in theoretical economic investigation. This paper has two major goals. The first is to describe what swinging is, discuss its economic relevance and single out the main characteristics of swinger behaviour. To this end, the Italian situation has been considered as a type of case study. The second goal is to use standard and less-standard tools from economic theory to propose some preliminary assessments of the causes and consequences of swinger couples’ behaviour. In this respect, some contributions on two-sided markets, hedonic adaptation approaches and equilibrium matching models have proved particularly useful.     

Between Transition and Enlargement: The Composition of Consumption in European Households

The article aims to specifically consider the effect of the enlargement of markets, resulting from the process of transition in Central and Eastern European countries, on the structure of household consumption. On the basis of a discriminatory analysis performed on recent data published by OECD and Eurostat, this study proposes to address three main questions: if during transition the household consumption patterns, measured by budget shares, have changed; if from this point of view, Central and Eastern European countries are similar between them and diverge from Western ones; if today there are any signs of convergence between the two groups of countries. The dissimilarity in budget share in Eastern and Western countries is proven and persistent, appearing greater in real terms than in nominal ones. On the one hand, Engel’s law is confirmed, given that at lower income levels the percentage of food consumption is greater, even though in real terms the absolute level of consumption of food has, in most cases, been reduced. On the other hand, the historical experience of Eastern countries is evident in the prolonged productive-distributive role of the State, especially in the field of essential services: home, schooling, and health.     

Providing social security in a context of change: Experience and challenges in Latin America

Over the past two decades Latin America has experienced major demographic, economic and social changes. The trend towards accelerated ageing of the population in most countries, together with the financial restrictions faced by social protection systems, has brought sweeping changes in pension programmes. The new demographic and labour context presents challenges for these new programmes which, unless they make the necessary adaptations, will definitely be unable to attain their stated objective of providing universal coverage and eliminating poverty in old age. This article offers a general discussion of the processes that the region is undergoing, as well as the limitations and challenges imposed by existing welfare systems. Finally, it examines the options available to retain the objective of universal coverage and thus ensure the economic needs of the elderly population.     

Boundaries of the business model within business groups

Scholars have sought various ways to find out how financial performance of the firm can be affected by its business model (BM). However, to date academic literature has focused attention on the “firm” as a unit of analysis without clearly defining the boundaries of the reporting entity to which the BMs refer. The aim of this paper is to investigate what are the boundaries of the BM of the affiliated-group companies and how the degree of independence of BMs is measured within the business group. The contribution of the paper is in using the BM concept to expound and criticise the assumptions in economic analysis and accounting standards that groups of companies are economic units that optimise economic income of the group as a whole and that the financial statements of individual subsidiaries, sub-groups and the group as a whole report the value generated by the group.     

Outlier detection in contingency tables based on minimal patterns

A new technique for the detection of outliers in contingency tables is introduced, where outliers are unusual cell counts with respect to classical loglinear Poisson models. Subsets of cell counts called minimal patterns are defined, corresponding to non-singular design matrices and leading to potentially uncontaminated maximum-likelihood estimates of the model parameters and thereby the expected cell counts. A criterion to easily produce minimal patterns in the two-way case under independence is derived, based on the analysis of the positions of the chosen cells. A simulation study and a couple of real-data examples are presented to illustrate the performance of the newly developed outlier identification algorithm, and to compare it with other existing methods.