Flexible Tweedie regression models for continuous data

Tweedie regression models (TRMs) provide a flexible family of distributions to deal with non-negative right-skewed data and can handle continuous data with probability mass at zero. Estimation and inference of TRMs based on the maximum likelihood (ML) method are challenged by the presence of an infinity sum in the probability function and non-trivial restrictions on the power parameter space. In this paper, we propose two approaches for fitting TRMs, namely quasi-likelihood (QML) and pseudo-likelihood (PML). We discuss their asymptotic properties and perform simulation studies to compare our methods with the ML method. We show that the QML method provides asymptotically efficient estimation for regression parameters. Simulation studies showed that the QML and PML approaches present estimates, standard errors and coverage rates similar to the ML method. Furthermore, the second-moment assumptions required by the QML and PML methods enable us to extend the TRMs to the class of quasi-TRMs in Wedderburn's style. It allows to eliminate the non-trivial restriction on the power parameter space, and thus provides a flexible regression model to deal with continuous data. We provide an R implementation and illustrate the application of TRMs using three data sets.     

A Multi Sited Approach to Analysis of Destination Immigration Data: An Asian Example

There has been a bias in standard international migration data collection and research toward immigration and destinations while emigration origins have been neglected. This has hampered our ability to provide a substantial empirical base for migration and development policy decision making in origin areas. While improvement of migration data collection in origin countries remains an important priority, this paper argues that much can be learned about emigration from low income countries from immigration data in high income destinations. Migration stock and flow data from Australia are used to provide information on the scale and nature of movement between Asia and Australia. It establishes that there are important but different flows in both directions which belie traditional conceptualisations of south‐north migration and this has significant implications for the effects of migration on economic development.     

The Gamma-count distribution in the analysis of experimental underdispersed data

Event counts are response variables with non-negative integer values representing the number of times that an event occurs within a fixed domain such as a time interval, a geographical area or a cell of a contingency table. Analysis of counts by Gaussian regression models ignores the discreteness, asymmetry and heteroscedasticity and is inefficient, providing unrealistic standard errors or possibly negative predictions of the expected number of events. The Poisson regression is the standard model for count data with underlying assumptions on the generating process which may be implausible in many applications. Statisticians have long recognized the limitation of imposing equidispersion under the Poisson regression model. A typical situation is when the conditional variance exceeds the conditional mean, in which case models allowing for overdispersion are routinely used. Less reported is the case of underdispersion with fewer modeling alternatives and assessments available in the literature. One of such alternatives, the Gamma-count model, is adopted here in the analysis of an agronomic experiment designed to investigate the effect of levels of defoliation on different phenological states upon the number of cotton bolls. Data set and code for analysis are available as online supplements. Results show improvements over the Poisson model and the semi-parametric quasi-Poisson model in capturing the observed variability in the data. Estimating rather than assuming the underlying variance process leads to important insights into the process.     

The Satisfaction with Sex Life Across the Adult Life Span

Three separate issues concerning the relation between age and satisfaction with sex life are addressed in this article. The first issue was concerned with the age generalizability of the factor structure produced by responses to the Satisfaction with Sex Life Scale (SWSLS). The second issue was to examine whether there were differences in the satisfaction with sex life according to certain background characteristics, namely age. Finally, the relationship between scores on the SWSLS with those on other relational constructs was explored. Data collection involved completion of a questionnaire. The sample consisted of 1,144 participants. The mean ages of the sample were 38.99 years in (SD = 16.91); ages ranged from 20 to 80. The data indicated that the factor structure of responses to the SWSLS were highly similar through adult life. Religious involvement, marital status, and love status influenced satisfaction with sex life. Expected correlations with measures of other relationship constructs were found. The strongest predictor of satisfaction with sex live across the adult life span was love satisfaction. Suggestions concerning the use of the SWSLS for research and clinical purposes are offered.     

Likelihood analysis for a class of beta mixed models

Beta regression is a suitable choice for modelling continuous response variables taking values on the unit interval. Data structures such as hierarchical, repeated measures and longitudinal typically induce extra variability and/or dependence and can be accounted for by the inclusion of random effects. In this sense, Statistical inference typically requires numerical methods, possibly combined with sampling algorithms. A class of Beta mixed models is adopted for the analysis of two real problems with grouped data structures. We focus on likelihood inference and describe the implemented algorithms. The first is a study on the life quality index of industry workers with data collected according to an hierarchical sampling scheme. The second is a study assessing the impact of hydroelectric power plants upon measures of water quality indexes up, downstream and at the reservoirs of the dammed rivers, with a nested and longitudinal data structure. Results from different algorithms are reported for comparison including from data-cloning, an alternative to numerical approximations which also allows assessing identifiability. Confidence intervals based on profiled likelihoods are compared with those obtained by asymptotic quadratic approximations, showing relevant differences for parameters related to the random effects. In both cases, the scientific hypothesis of interest was investigated by comparing alternative models, leading to relevant interpretations of the results within each context.     

The Saving for Every Child Program in Israel: an overview of a universal asset-building policy

ABSTRACT

In 2017, the Israeli government implemented a universal child development account programme – the Saving for Every Child Program (SECP) – which establishes a personal savings account for every Israeli child and provides monthly deposits until the child turns 18. The SECP has the potential to provide substantial assets when children reach adulthood, but the benefits depend on parents’ investment choices. The unique programme’s nature presents opportunities to learn from its implementation. This paper provides a comprehensive overview of the SECP, its legislative history, early findings from its implementation, and recommendations that may improve programme participation and outcomes across population groups.     

Aging in the Third World

The relationships between the generations in Third World countries are changing as migration and industrialization erode traditional family responsibilities for supporting the elderly. It is no longer possible to assume that, as a matter of course, old people will be looked after by their families. Social change leads to an eroding of the support systems. The author finds growing evidence of this breakdown in Asia, particularly in Singapore, Hong Kong, and other highly industrialized centers. Singapore, for example, has reinstituted the compulsory study of filial piety in an attempt to push the younger generation into assuming its traditional responsibility toward the old. There has also been a significant decline in the status, prestige, and support given old people in Indonesia, although politicans insist that the family will always take care of its elderly. 2 reasons for this breakdown are 1) the impact of the mass media and 2) the increasing involvement of the younger generation in non-agricultural jobs which often involve a move to the city and away from dependence on a patriarch. Many Third World countries are in a twilight stage, between the traditionally strong structure of family support and government systems of social security.