Climate,agriculture, and hunger: statistical prediction of undernourishment using nonlinear regression and data-mining techniques

An estimated 1 billion people suffer from hunger worldwide, and climate change, urbanization, and globalization have the potential to exacerbate this situation. Improved models for predicting food security are needed to understand these impacts and design interventions. However, food insecurity is the result of complex interactions between physical and socio-economic factors that can overwhelm linear regression models. More sophisticated data-mining approaches could provide an effective way to model these relationships and accurately predict food insecure situations. In this paper, we compare multiple regression and data-mining methods in their ability to predict the percent of a country's population that suffers from undernourishment using widely available predictor variables related to socio-economic settings, agricultural production and trade, and climate conditions. Averaging predictions from multiple models results in the lowest predictive error and provides an accurate method to predict undernourishment levels. Partial dependence plots are used to evaluate covariate influence and demonstrate the relationship between food insecurity and climatic and socio-economic variables. By providing insights into these relationships and a mechanism for predicting undernourishment using readily available data, statistical models like those developed here could be a useful tool for those tasked with understanding and addressing food insecurity.     

Asymptotic behavior of RA-estimates in autoregressive 2D processes

In this work we study the asymptotic behavior of a robust class of estimators of the coefficient of a AR-2D process. We establish the precise conditions for the consistency and asymptotic normality of the RA estimator. The AR-2D model has many applications in image modeling and statistical image processing, therefore the relevance of knowing such properties. The adequacy of the AR-2D model is analyzed with real images; we also show the impact of contamination and the capability of the RA estimator to produce useful results even in the presence of spurious data.     

A Dynamic Model of Investment in the U.S. Beef-Cattle Industry

Reproduction constraints lead to some a priori information that may prove valuable in econo- metrically modeling inventory dynamics within the U.S. cattle herd. The distributed-lag models estimated for animal inventories suggest an implicit incorporation of the age distribution of the herd that is crucial to understanding the retention/culling (investment) decisions. The estimated equations are validated using post-sample observations that were withheld prior to estimation. The final-form dynamic equations have complex roots and protracted price and investment effects. The parameter estimates are used to calculate intermediate and long-run elasticities at the means of relevant variables.     

A program of research with Hispanic and African American families: three decades of intervention development and testing influenced by the changing cultural context of Miami

In this article we summarize work with poor, inner-city Hispanic and African American families conducted at the University of Miami Center for Family Studies. We elucidate ways in which this research program has paralleled the treatment development paradigm and has been responsive to changes in local demographics. Specific cultural issues pertaining to Hispanics and African Americans are discussed in light of treatment development and implementation. Future directions and challenges for working with poor, inner-city minority families are addressed.     

Trauma symptoms, sexual behaviors, and substance abuse: correlates of childhood sexual abuse and HIV risks among men who have sex with men

Childhood sexual abuse is associated with high-risk sexual behavior in men who have sex with men. This study examined psychological and behavioral correlates of HIV risk behavior associated with childhood sexual abuse in a sample of men who have sex with men. Men attending a large gay pride event (N = 647) completed anonymous surveys that assessed demographic characteristics, childhood sexual abuse history, symptoms of dissociation and trauma-related anxiety, borderline personality characteristics, substance use, and sexual risk behavior. Results indicated that men who have a history of childhood sexual abuse were more likely to: engage in high-risk sexual behavior (i.e., unprotected receptive anal intercourse), trade sex for money or drugs, report being HIV positive, and experience non-sexual relationship violence. Results of this study extend previous research to show that men who have sex with men and who have a history of child sexual abuse are more likely to be at high risk for HIV infection.     

The Measurement of Intellectual Influence

This paper examines the problem of measuring intellectual influence based on data on citations between scholarly publications. We follow an axiomatic approach and find that the properties of invariance to reference intensity, weak homogeneity, weak consistency, and invariance to splitting of journals characterize a unique ranking method. This method is different from those regularly used in economics and other social sciences.     

Development of Sexual Expectancies among Adolescents: Contributions by Parents,Peers and the Media

To expand the scant research on sexual expectancies development among non–sexually active adolescents, we examined the relationship between adolescents' exposure to four socializing agents—mother/female guardian, father/male guardian, peers, and television programs with high sexual content—and their endorsement of four sexual expectancies: social benefit, pleasure, social risk, and health risk. Data are from Waves 2 and 3 of a three-wave annual longitudinal study conducted among California adolescents, the majority of whom were not sexually active (N = 914, 84%). Structural equation models were conducted to examine cross-sectional and longitudinal associations between the socializing agents and the sexual expectancies. Cross-sectional results indicate associations between peer sexual communication and social benefit, pleasure, and social risk expectancies. A positive association was found between exposure to music videos and social benefit expectancies, and a negative association was found between exposure to music videos and health risk expectancies. Longitudinal results suggest that communication with peers positively predicted pleasure expectancies and negatively predicted social risk expectancies. No other socializing agents were associated with any sexual expectancies. An invariance test found that significant correlations were similar across the different age groups. Results suggest that efforts to support positive sexual decision making among non–sexually active adolescents should target peer sexual communication.     

Remittances and labour market outcomes: Evidence from Mexico

The effects of remittances on labour market outcomes have been studied by many researchers, primarily using micro‐level data. While a few studies have also used macro‐level data, they suffer from endogeneity bias due to the inclusion of remittances in their estimations. The present study attempts to fill the gap in the literature by using a set of panel data of Mexican states and by addressing the endogeneity bias with a system GMM (generalized method of moments) estimator. The main conclusions are that remittances increase labour force participation rates and reduce median hours worked, critical employment and unemployment duration.