Log-linear models for mutations in the HIV genome

We discuss a general application of categorical data analysis to mutations along the HIV genome. We consider a multidimensional table for several positions at the same time. Due to the complexity of the multidimensional table, we may collapse it by pooling some categories. However, the association between the remaining variables may not be the same as before collapsing. We discuss the collapsibility of tables and the change in the meaning of parameters after collapsing categories. We also address this problem with a log-linear model. We present a parameterization with the consensus output as the reference cell as is appropriate to explain genomic mutations in HIV. We also consider five null hypotheses and some classical methods to address them. We illustrate methods for six positions along the HIV genome, through consideration of all triples of positions.     

Job bust, baby bust?: Evidence from Spain

The unemployment rate in Spain has been exceptionally high for more than two decades by now. During the same period the fertility rate dropped dramatically reaching the lowest level in the world. In this study we look for evidence of a link between the `unemployment crisis' and the `fertility crisis' in Spain. We examine the factors that affect individuals' ages at marriage and childbirth, focusing on the effects of male employment status. Our results show that spells of non-employment have a strong negative effect on the hazard of marriage. We also find negative (but smaller) effects of part-time or temporal employment on the hazard of marriage. The estimated direct effects of joblessness and part-time work on birth hazards conditional on marriage are smaller and/or not significant for most birth intervals and sample groups. Simulations based on the estimated models confirm the potential for large `delaying' effects of joblessness on marriage. However, the delaying effect is not so large in simulations which control for the actual incidence of non-employment in the sample. Received: 7 January 1999/Accepted: 7 March 2000     

Economic well‐being of low‐income single‐mother families following welfare reform in the USA

This study explored changes in net disposable income for low‐income single‐mother families before and after the 1996 welfare reform in the USA. Although many studies on welfare reform have focused on employment or total family income as a way to measure low‐income single‐mother families’ economic well‐being, little is known about their net income after expenses related to entering the workforce. This study analyzed net disposable income after tax deductions and childcare costs to provide a more accurate understanding of income changes using data from the Survey of Income and Program Participation conducted by the US Census Bureau. The results revealed that while low‐income single mothers were working more after welfare reform, their net disposable income decreased during this time because their earnings were low and offset by an increase in childcare costs and a decline in means‐tested benefits, including Temporary Assistance for Needy Families benefits. Key Practitioner Message: ● To understand effects of the 1996 welfare reform on low‐income families’ economic well‐being; ● To understand comprehensive income sources and work related expenses of low‐income families; ● To provide policy suggestions for comprehensive childcare subsidies to support low‐income single mothers’ employment.     

Multidimensional Inequality in South Korea: An Empirical Analysis

The objective of this study is to review the theoretical limitations of single dimensional approaches for measuring inequality and to prove the effectiveness and practicality of the concept of “multidimensional inequality” by analyzing the inequality embedded in Korean society. This study constitutes nine dimensions of inequality (income, education, health, employment, social capital, leisure, work‐family reconciliation, housing, and social security) and analyzes inequality through the lens of each dimension by using data from of the first to fifth wave of the Korea Welfare Panel Study. The findings show a high degree of correlation among the dimensions of income, education, health, and social capital. However, work‐family reconciliation and housing have a relatively low correlation with income and the other dimensions. Second, multidimensional disparities were found between the groups of gender, age, and region. In conclusion, this study found a high degree of overlap between the concepts of income‐oriented inequalities and the multidimensional inequality approach. By capturing the notions of the multidimensional disparities that exist in each of the different groups, this study confirmed the effectiveness of multidimensional inequality as a useful concept for informing the creation of social policy intervention to alleviate inequality.     

Group and within-group variable selection for competing risks data

Variable selection in the presence of grouped variables is troublesome for competing risks data: while some recent methods deal with group selection only, simultaneous selection of both groups and within-group variables remains largely unexplored. In this context, we propose an adaptive group bridge method, enabling simultaneous selection both within and between groups, for competing risks data. The adaptive group bridge is applicable to independent and clustered data. It also allows the number of variables to diverge as the sample size increases. We show that our new method possesses excellent asymptotic properties, including variable selection consistency at group and within-group levels. We also show superior performance in simulated and real data sets over several competing approaches, including group bridge, adaptive group lasso, and AIC / BIC-based methods.     

An analysis on basic income: Evidence using data from experimental projects throughout the world

Basic income was a hot issue in the recent Korean presidential election. Its pros and cons were used to scramble for the electorate's votes. However, their arguments largely relied on political rhetoric and lacked scientific facts. The problem is that politics without the backing of science is not only prone to a misguided conviction but also going to deal a blow to the future development of basic income. This study aims to narrow the gap between rhetoric and facts through evidence-based research on basic income. By employing methods of fact-finding and effect evaluation, we analyze using four aspects of assessment, namely, general information about basic income experiments; details on the experiments; development of the experiments; and the effect of the experiments. Basic income-related data are drawn from the World Bank and the Basic Income Laboratory at Stanford University. Significant results of the review are that some positive effects were identified at the micro level but any meaningful macro-level impact was impossible to confirm. To sum up, the outcomes are so erratic that it is difficult to detect any clear pattern in policy impacts. To approach basic income more scientifically, further research is urgently needed.     

An Industrial Ocean-Cargo Shipping Problem

This paper reports the modeling and solution of an industrial ocean-cargo shipping problem. The problem involves the delivery of bulk products from an overseas port to transshipment ports on the Atlantic Coast, and then over land to customers. The decisions made include the number and the size of ships to charter in each time period during the planning horizon, the number and location of transshipment ports to use, and transportation from ports to customers. The complexity of this problem is compounded by the cost structure, which includes fixed charges in both ship charters and port operations. Such a large scale, dynamic, and stochastic problem is reduced to a solvable stationary, deterministic, and cyclical model. The process of modeling the problem and the solution of the resultant mixed integer program are described in detail. Recommendations from this study have been implemented.