196,298 research outputs found
Correction to: Safety of laparoscopic compared to open right hepatectomy after portal vein occlusion: results from a multicenter study (Surgical Endoscopy, (2025), 39, 3, (1839-1847), 10.1007/s00464-025-11532-8)
No full textThe original online version of this article was revised to correct the presentation of the name of coauthor Nadia Russolillo, and to correct the affiliation information for corresponding author Serena Langella. The original article has been corrected
On the use of Structural Equation Models and PLS Path Modeling to build composite indicators
No full textNowadays there is a pre-eminent need to measure very complex phenomena like poverty, progress, well-being, etc. As is well known, the main feature of a composite indicator is that it summarizes complex and multidimensional issues. Thanks to its features, Structural Equation Modeling seems to be a useful tool for building systems of composite indicators. Among the several methods that have been developed to estimate Structural Equation Models we focus on the PLS Path Modeling approach (PLS-PM), because of the key role that estimation of the latent variables (i.e. the composite indicators) plays in the estimation process. In this work, first we present Structural Equation Models and PLS-PM. Then we provide a suite of statistical methodologies for handling categorical indicators in PLS-PM. In particular, in order to take categorical indicators into account, we propose to use a modified version of the PLS-PM algorithm recently presented by Russolillo [2009]. This new approach provides a quantification of the categorical indicators in such a way that the weight of each quantified indicator is coherent with the explicative ability of the corresponding categorical indicator. To conclude, an application involving data taken from a paper by Russet [1964] will be presented.PLS Path Modeling,Categorical Indicators,Structural Equation Modeling,Composite Indicators
Internal risk control by solvency measures
No full textThe paper deals with the solvency analysis through internal models in the case of a portfolio of life annuities, focusing on the interplay between stochastic interest rate dynamics and the survival evolution in time. This specific aspect is investigated basing the survival death rates on Poisson Lee Carter model approached according to the Iterative Procedure and two simulated approaches on the Poisson Lee Carter: the Standard Procedure and the Stratified Sampling Procedure. The financial aspect, particularly notable in portfolios with long duration and multiplicity of payments as in the considered case, is tackled assuming different stochastic hypotheses on the interest rates evolution. Aim of the paper is to deepen the reaction of solvency measures as the surplus index and the ruin probability to the specific financial and demographic scenario. The indexes are studied in different loading factor assumptions and several numerical applications illustrate the model setup
On the evolution of the gender gap in life expectancy at normal retirement age for OECD countries
No full textPopulation aging is evolving at different rates across countries and over time, and it
represents a long-term challenge for both the sustainability of pension schemes and for
the realization of public intergenerational transfers. In this context, this work focuses on
gender differences in survival at older ages. Specifically, we implement a comparative
analysis of OECD countries to assess the adequacy of the corresponding gender-specific
normal retirement age when faced with growing life expectancy. The analysis hinges on
several graphical representations and is motivated by recent findings on Italian longevity
to determine optimal retirement age shifts necessary to match growing life expectancy
at older ages while accounting for model risk for mortality projections. Our analysis determines—
at the country level—the extent to which adjustments to the normal retirement
age are advisable for the sustainability of the intergenerational paradigm for pensions.
The study considers males and females separately because most of these countries are
characterized by aging societies where men and women have different crucial characteristics,
including life expectancy. It is therefore important that policymakers have information
on the future evolution of the longevity gender gap so they will be able to apply
policies that preserve the principles of equality and solidarity and reduce the pension
gender gap. We find groups of countries where gender gap in life expectancy follows the
same dynamics
Immunological detection of m- and μ-calpains in the skeletal muscle of Marchigiana cattle.
No full textCalpains are Ca2+-dependent proteases able
to cleave a large number of proteins involved
in many biological functions. Particularly, in
skeletal muscle they are involved in meat tenderizing
during post mortem storage. In this
report we analyzed the presence and expression
of μ- and m-calpains in two skeletal muscles
of the Marchigiana cattle soon after
slaughter, using immunocytochemical and
immunohistochemical techniques, Western
blotting analysis and Casein Zymography.
Therefore, the presence and the activity of
these proteases was investigated until 15th day
post mortem during normal process of meat
tenderizing. The results showed m- and μ-calpain
immunosignals in the cytoplasm both
along the Z disk/I band regions and in the form
of intracellular stores. Moreover, the expression
level of μ-calpain but not m-calpain
decreased after 10 days of storage. Such a
decrease in μ-calpain was accompanied by a
gradual reduction of activity. On the contrary,
m-calpain activity persisted up to 15 days of
post mortem storage. Such data indicate that
expression and activity of both μ-calpain and
m-calpain analyzed in the Marchigiana cattle
persist longer than reported in literature for
other bovines and may be related to both the
type of muscle and breed examined
Measuring mortality heterogeneity in pension annuities
No full textPension plan sponsors face a myriad of risks, one of which is longevity risk that arises from the increasing life expectancy trends among pensioners. Traditionally, plan sponsors manage longevity risk by forecasting the mortality rates. However, recent acceleration in longevity improvement forces the insurance companies to assess accurately the survival trend, in order to avoid paying much longer than expected. As regards the mortality trend we have to empathize different features with respect to mortality due to different race, ethnicity, income, wealth, marital status, educational attainment and so on. The mortality heterogeneity tends to determine a phenomenon termed as overdispersion, according to which the variance compared to the mean increases. Some authors take into account the mortality overdispersion by estimating the parameter in a mixed Poisson model. In the current literature, there are several papers which have considered the modelling and forecasting of population mortality using the Lee-Carter framework. In this paper, we propose an extended version of the model under consideration, in order to capture the phenomenon of the heterogeneity in mortality trend, by using the geographical stratification of the population. Diagnostic plots are provided to show the results and actuarial application is performed in a context of pension products
Lee Carter error matrix simulation: heteroschedasticity impact on actuarial valuations
No full textRecently a number of approaches have been developed for forecastingmortality. In
this paper, we consider the Lee-Carter model and we investigate in particular the hypothesis
about the error structure implicitly assumed in the model specification, i.e., the errors are homoschedastic.
The homoschedasticity assumption is quite unrealistic, because of the observed
pattern of the mortality rates showing a different variability at old ages than younger ages.
Therefore, the opportunity to analyse the robustness of estimated parameter is emerging. To
this aim,we proposean experimental strategy in order to assessthe robustness of the Lee-Carter
model by inducing the errors to satisfy the homoschedasticity hypothesis.Moreover, we apply
it to a matrix of Italian mortality rates. Finally, we highlight the results through an application
to a pension annuity portfolio
The mortality of the Italian population: Smoothing techniques on the Lee-Carter Model
No full textSeveral approaches have been developed for forecasting mortality using
the stochastic model. In particular, the Lee–Carter model has become widely
used and there have been various extensions and modifications proposed to
attain a broader interpretation and to capture the main features of the dynamics
of the mortality intensity. Hyndman–Ullah show a particular version of
the Lee–Carter methodology, the so-called Functional Demographic Model,
which is one of the most accurate approaches as regards some mortality data,
particularly for longer forecast horizons where the benefit of a damped trend
forecast is greater. The paper objective is properly to single out the most suitable
model between the basic Lee–Carter and the Functional Demographic
Model to the Italian mortality data. A comparative assessment is made and
the empirical results are presented using a range of graphical analyses
- …
