Imposing and Testing for Shape Restrictions in Flexible Parametric Models

In many economic models, theory restricts the shape of functions, such as monotonicity or curvature conditions. This article reviews and presents a framework for constrained estimation and inference to test for shape conditions in parametric models. We show that “regional” shape-restricting estimators have important advantages in terms of model fit and flexibility (as opposed to standard “local” or “global” shape-restricting estimators). In our empirical illustration, this is the first article to impose and test for all shape restrictions required by economic theory simultaneously in the “Berndt and Wood” data. We find that this dataset is consistent with “duality theory,” whereas previous studies have found violations of economic theory. We discuss policy consequences for key parameters, such as whether energy and capital are complements or substitutes.     

“To get the word out”: LGBTQ+ Young adults’ motivations for participating in qualitative research studies

Understanding why socially marginalized individuals, such as lesbian, gay, bisexual, transgender and/or queer (LGBTQ+) people, participate in research can improve qualitative research designs, as well as social services and policies. In providing a participant-centered foundation, we interviewed 65 LGBTQ+ young adults and asked “Why are certain LGBTQ+ young adults motivated to engage in qualitative social science studies?” Many LGBTQ+ young people said they were committed to enacting social change and promoting advocacy. Participants also highlighted supporting scientific research and knowledge production. Finally, LGBTQ?+ participants engaged with research to introspectively analyze their identity development processes. These findings can facilitate access to socially vulnerable and underrepresented groups through a methodological focus on participant benefits.     

Optimization problems with color-induced budget constraints

In 1984, Gabow and Tarjan provided a very elegant and fast algorithm for the following problem: given a matroid defined on a red and blue colored ground set, determine a basis of minimum cost among those with k red elements, or decide that no such basis exists. In this paper, we investigate extensions of this problem from ordinary matroids to the more general notion of poset matroids which take precedence constraints on the ground set into account. We show that the problem on general poset matroids becomes -hard, already if the underlying partially ordered set (poset) consists of binary trees of height two. On the positive side, we present two algorithms: a pseudopolynomial one for integer polymatroids, i.e., the case where the poset consists of disjoint chains, and a polynomial algorithm for the problem to determine a minimum cost ideal of size l with k red elements, i.e., the uniform rank-l poset matroid, on series-parallel posets.     

Rethinking twins and environments: possible social sources for assumed genetic influences in twin research

A central sociological problem is the extent to which genetics and the environment influence human behavior. Studies of twins are a core method in attempts to disentangle and to determine the comparative strength of genetic and environmental influences on psychosocial outcomes. A critical assumption of twin studies is that both monozygotic "identical" twins and dizygotic "fraternal" twins share common social environments. Therefore, any greater similarity of monozygotic than dizygotic twins is attributed to genetic influences. This paper tests the equal environment assumption by examining the extent to which greater concordance of adolescent monozygotic compared to dizygotic twins results from social, as well as genetic, influences. Bivariate comparisons indicate that monozygotic twins show greater similarity than dizygotic twins in socially-based characteristics including physical attractiveness, time spent in each other's company, the overlap in friendship networks, and friends' use of alcohol. Multivariate analyses indicate that measures of the social environment sometimes reduce or eliminate apparent genetic effects. In comparison with genetic indicators, social variables are usually stronger predictors of depression and alcohol use and abuse. These findings suggest that past twin studies could overstate the strength of genetic influences because some similarities in behavior among monozygotic compared to dizygotic twins stem from social influences.     

Risk of Extreme Events in Multiobjective Decision Trees Part 1. Severe Events

Earlier work with decision trees identified nonseparability as an obstacle to minimizing the conditional expected value, a measure of the risk of extreme events, by the well-known method of averaging out and folding back. This first of two companion papers addresses the conditional expected value that is defined as the expected outcome assuming the exceedance of a threshold β, where β is preselected by the decision maker. An approach is proposed to overcome the need to evaluate all policies in order to identify the optimal policy. The approach is based on the insight that the conditional expected value is separable into two constituent elements of risk and can thus be optimized along with other objectives, including the unconditional expected value of the outcome, by using a multiobjective decision tree. An example of sequential decision making for improving highway capacity is given.     

Homelessness as one component of housing instability and its impact on the development of children in poverty

The number of families with children living in poverty and experiencing housing instability and homelessness has increased dramatically over the last two decades. Current public policy decisions will lead to further increases. Understanding the impact of this instability on the emotional, behavioral, and cognitive development of children is imperative. Few studies critically examine the effects of instability on both domiciled and homeless children. This research examined the effects of homelessness and housing instability on 133 children 8 to 12 years of age living in poverty. Results indicate that whether a child is currently homeless is not as significant as overall stability which may have a long ranging effect on a child's future development.     

The Distribution of the German Public–Private Wage Gap

This paper provides a distributional analysis of the public–private sector wage gap in Germany from 1984 to 1996. The public sector wage distribution is generally less dispersed than the private sector wage distribution. The raw wage differential is positive for males who are at the lower tail of the male wage distribution and negative at the upper tail. In contrast, females enjoy positive wage gaps along most part of the wage distribution. A decomposition analysis reveals that the male wage premium, i.e. the part of the wage gap not accounted for by differences in observable characteristics, is uniformly negative, whereas the female wage premium is positive.