Parametric Estimation for Subordinators and Induced OU Processes

Abstract.  Consider a stationary sequence of random variables with infinitely divisible marginal law, characterized by its Lévy density. We analyse the behaviour of a so-called cumulant M-estimator, in case this Lévy density is characterized by a Euclidean (finite dimensional) parameter. Under mild conditions, we prove consistency and asymptotic normality of the estimator. The estimator is considered in the situation where the data are increments of a subordinator as well as the situation where the data consist of a discretely sampled Ornstein–Uhlenbeck (OU) process induced by the subordinator. We illustrate our results for the Gamma-process and the Inverse-Gaussian OU process. For these processes we also explain how the estimator can be computed numerically.     

CURRENT STATUS AND RIGHT-CENSORED DATA STRUCTURES WHEN OBSERVING A MARKER AT THE CENSORING TIME

We study nonparametric estimation with two types of data structures. In the first data structure n i.i.d. copies of (C, N(C)) are observed, where N is a finite state counting process jumping at time-variables of interest and C a random monitoring time. In the second data structure n i.i.d. copies of (C ∧ T, I (T ≤ C), N(C ∧ T)) are observed, where N is a counting process with a final jump at time T (e.g., death). This data structure includes observing right-censored data on T and a marker variable at the censoring time.In these data structures, easy to compute estimators, namely (weighted)-pool-adjacent-violator estimators for the marginal distributions of the unobservable time variables, and the Kaplan-Meier estimator for the time T till the final observable event, are available. These estimators ignore seemingly important information in the data. In this paper we prove that, at many continuous data generating distributions the ad hoc estimators yield asymptotically efficient estimators of [Formula: see text]-estimable parameters.     

MANAGING THE ENVIRONMENTAL EXTERNALITIES OF TRAFFIC LOGISTICS: THE ISSUE OF EMISSIONS

Companies are increasingly being held accountable for the life‐cycle impact of their products and services. Transportation is frequently a major component of this life‐cycle impact. Hence, to reduce total environmental impact, logistics managers will have to become more sophisticated in their understanding of how they can reduce the environmental impact of their transportation operations, without negatively affecting the cost or effectiveness of these operations. In line with this mandate, we quantify the dynamic impact of road vehicles on the environment. In most emission models, a constant speed is used depending only on the specific road type. Using such a model will lead to an underestimation of the effective emissions. It turns out that the differences with a more realistic dynamic assessment model are significant. The analysis here suggests that the policy consequences of these differences for both public sector managers and private companies are potentially quite important.     

Transnational activities and aspirations of irregular migrants in Belgium and the Netherlands

The literature on immigrant transnationalism and on irregular immigration suggests irregular migrants engage relatively little in transnational activities because of the obstacles associated with their legal and economic statuses. Drawing on participant observation and in‐depth interviews with a diverse population of irregular migrants in Belgium and the Netherlands, however, I shall demonstrate in this article that irregular migrants do indeed engage in various transnational activities. Moreover, I argue that a focus on aspirations helps to understand why irregular migrants either do or do not engage in specific transnational activities. Distinguishing between investment, settlement and legalization aspirations, I analyse whether and for what reasons irregular migrants carry out economic, social and political transnational activities. I conclude that future research on transnationalism and on the incorporation of irregular and regular migrants alike could benefit from contextualizing the agency of migrants by taking their aspirations into account.