Ricerc@Sapienza

The forward order assumption postulates that the ranking process of the
items is carried out by assigning the positions from the top (most-liked) to the bottom
(least-liked) alternative. This assumption has been recently relaxed in the Extended
Plackett-Luce model (EPL) through the introduction of the discrete reference
order parameter, describing the rank attribution path. By starting from two formal
properties of the EPL, we derive novel diagnostic tools for testing appropriateness of

We test the hypothesis that commodity prices tend to decline relatively to manufactured goods prices using a panel cointegration bootstrap test. The hypothesis does not hold for 1950–1980, and it does for 1950–2011 for agricultural products but not for Metals.

Resampling methods are widely studied and increasingly employed in applied
research and practice. When dealing with complex sampling designs, common
resampling techniques require to adjust non-integer sampling weights in order to
construct the so called “pseudo-population” where to perform the actual resampling.
In particular, to lighten the computational burden, it is commonly suggested
to round resampling weights to the nearest integer. This practice, however, has
been empirically shown to be harmful under general designs. Here we develop

In this paper, a class of resampling techniques for finite populations under pps sampling design is introduced. The basic idea on which they rest is a two-step procedure consisting in: (i) constructing a pseudo-population" on the basis of sample data; (ii) drawing a sample from the predicted population according to an appropriate resampling design. From a logical point of view, this approach is essentially based on the plug-in principle by Efron, at the "sampling design level". Theoretical justifications based on large sample theory are provided.

This paper focuses on the estimation of the concentration curve of a finite population, when data are collected according to a complex sampling design with different inclusion probabilities. A (design-based) Hájek type estimator for the Lorenz curve is proposed, and its asymptotic properties are studied. Then, a resampling scheme able to approximate the asymptotic law of the Lorenz curve estimator is constructed.

The paper estimates the standard cost in Italian regional public rail passenger transport services (LPTR), depending on service characteristics. The results highlight the crucial role of: number of seats per ride, commercial speed, service size and length of rail tracks. The model also shows the positive link between investment in rolling stock and the unit cost of the service.