How trade/GNP ratio decreases with country size

The ratio of a country's foreign trade (i.e., exports plus imports) to its GNP has a known tendency to decrease with country size. Previous studies have used a single year's data; but trade fluctuates greatly from year to year. This paper makes available a compilation of 1953–1972 export/GNP and import/GNP figures for 110 countries. The average import/GNP figure is found to correlate strongly with population size; the simple expression, Imports/GNP = 40 $\text{P}{}^{\mathrm{<mtext>?1</mtext><mtext>3</mtext>}}$, applies, within a factor of 2, in 94% of cases. No correlation with development level can be seen. The United States data throughout its history (1799–1972) follow the same inverse cube root pattern, but with a constant of 20 instead of 40. Correlation is much poorer in the case of export/GNP ration. Export and import figures are only marginally correlated to each other.     

Predicting distances using a linear model: the case of varietal distinctness

Differences between plant varieties are based on phenotypic observations, which are both space and time consuming. Moreover, the phenotypic data result from the combined effects of genotype and environment. On the contrary, molecular data are easier to obtain and give a direct access to the genotype. In order to save experimental trials and to concentrate efforts on the relevant comparisons between varieties, the relationship between phenotypic and genetic distances is studied. It appears that the classical genetic distances based on molecular data are not appropriate for predicting phenotypic distances. In the linear model framework, we define a new pseudo genetic distance, which is a prediction of the phenotypic one. The distribution of this distance given the pseudo genetic distance is established. Statistical properties of the predicted distance are derived when the parameters of the model are either given or estimated. We finally apply these results to distinguishing between 144 maize lines. This case study is very satisfactory because the use of anonymous molecular markers (RFLP) leads to saving 29% of the trials with an acceptable error risk. These results need to be confirmed on other varieties and species and would certainly be improved by using genes coding for phenotypic traits.     

On perfect simulation for some mixtures of distributions

This paper studies the implementation of the coupling from the past (CFTP) method of Propp and Wilson (1996) in the set-up of two and three component mixtures with known components and unknown weights. We show that monotonicity structures can be exhibited in both cases, but that CFTP can still be costly for three component mixtures. We conclude with a simulation experiment exhibiting an almost perfect sampling scheme where we only consider a subset of the exhaustive set of starting values.     

Avian Influenza in Vietnam: Chicken‐Hearted Consumers?

This study, based on quantitative and qualitative surveys conducted from July 2004 to September 2005, examines the perceptions of Hanoi consumers and their reactions to the Avian Influenza epizootic (H5N1). Hanoi consumers clearly link the risk of human contamination by the virus to the preparation and ingestion of poultry. During the first crisis, consumers reacted quickly and intensely (74% of them had already stopped eating poultry in January 2004). Nevertheless, once the crisis abated, they quickly resumed their consumption of poultry. This behavior corresponds to the pattern described by empirical studies of other crises, such as BSE. What is more surprising is the speed with which the different steps of this common pattern succeeded one another. It may be explained by a rapid decrease in risk anxiety. A logit model shows that, soon after the beginning of the crisis, AI risk anxiety was tempered by confidence in the information and recommendations issued by the government concerning AI and, in the long term, by a high perceived self-efficiency to deal with AI. Indeed, not only has poultry consumption been affected in terms of the quantity consumed, but alternative ways of selecting and preparing poultry have also been adopted as anti-risk practices. Risk communication strategies should take this into account, and rely on a previous assessment of consumer practices adopted to deal with the risk.     

Is the Way Young People Drive a Reflection of the Way Their Parents Drive? An Econometric Study of the Relation Between Parental Risk and Their Children's Risk

This article aims to investigate parental influence on high-risk behavior by young people. Although research on the topic of perception of risk demonstrates that it is socially constructed, the role of the family in this construction has rarely been studied. Using a French national survey of more than 1,200 young drivers between the ages of 18 and 25, and their parents, we attempt to understand the transmission of risk within families. Our econometric study shows that parents influence both the practices and representations of their children. When parental norms and values are transmitted, they are by no means accepted in a wholly passive way. Indeed, the parental model is in competition with other models that originate from both inside the family (brothers and sisters) and outside it (instructors). Furthermore, parental influence decreases over time as young people become more experienced drivers and construct their own identity with regard to risk.     

The Intervening Role of Relational Aggression between Psychological Control and Friendship Quality

This study investigated the associations among psychologically controlling parenting, relational aggression, friendship quality, and loneliness during adolescence. A model was proposed in which relational aggression plays an intervening role in the relations between both parental psychological control and friendship outcomes. In a sample comprised of middle adolescents and their parents, process analyses revealed that psychological control (indexed by parent and adolescent reports) positively predicted adolescents' self-reported relational aggression that, in turn, negatively predicted friendship quality and positively predicted loneliness. The model held for both mothers and fathers and was not moderated by adolescent gender. The discussion focuses on possible mechanisms explaining the relations among psychological control, relational aggression, and friendship outcomes.