Can Supersymmetry Naturally Explain the Positron Excess?

It has often been suggested that the cosmic positron excess observed by the HEAT experiment could be the consequence of supersymmetric dark matter annihilating in the galactic halo. Although it is well known that evenly distributed dark matter cannot account for the observed excess, if substantial amounts of local dark matter substructure are present, the positron flux would be enhanced, perhaps to the observed magnitude. In this paper, we attempt to identify the nature of the substructure required to match the HEAT data, including the location, size and density of any local dark matter clump(s). Additionally, we attempt to assess the probability of such substructure being present. We find that if the current density of neutralino dark matter is the result of thermal production, very unlikely ($\sim 10^{-4}$ or less) conditions must be present in local substructure to account for the observed excess.Comment: Version accepted by Physical Review

A look at long-term developments in the distribution of income

Developments in the distribution of income have received much attention over the past decade. Several analysts have argued that income gains have gone almost exclusively to the highest paid 20 percent of the population, leaving no gains to the remaining 80 percent. ; Joseph H. Haslag and Lori L. Taylor examine developments in income inequality over the past forty years and estimate which factors account for these changes over time. While some researchers have found that income distribution became more equal during the 1950s and 1960s and then less equal after the mid-1970s, Haslag and Taylor find evidence that an upward trend in income inequality has been occurring since the early 1950s. They also find that movements in the income inequality measure are mostly determined by persistence; that is, income inequality adjusts gradually. Demographic features account for nearly 25 percent of the variation in income inequality, while policy actions explain less than 15 percent.Income distribution

Low-powered incentives

We study low-powered incentives in a model that captures important features of workplaces in which incentive-pay approaches are minimally relevant. Our motivation is that incentive pay, while not rare, is clearly far less common than are agency problems: many firms with agency problems nonetheless pay fixed compensation and offer continued employment to all but those workers judged "unsatisfactory" according to largely subjective criteria. We find that low-powered incentives can achieve efficient outcomes in simple workplaces and function surprisingly well even when the environment is characterized by unobservable performance heterogeneity and a high degree of complementarity among workers.Wages

Economic models of employee motivation

Workers, being human beings, present employers with a range of tricky problems. Humans, unlike filing cabinets, can be crooked, subversive, surly, or indolent, even if they are paid on time. In this article we explore economists' main models of how compensation is used to address employee motivation and how these models help to explain puzzling features of the labor market.Wages ; Management ; Labor market

Valuable jobs and uncertainty

Little attention has been given to the link between variation in a firm's circumstances and the resolution of agency problems that pervade the relationship between a firm and its employees. We construct stochastic versions of standard efficiency-wage and performance-bonding models and find that this connection has important and apparently inescapable consequences. Compensation levels depend on characteristics of the firm. The possibility of the firm's exit drive an important counterfactual prediction in both classes of model: compensation rises in dying firms. This result illustrates the need for careful attention to the circumstances under which valuable jobs are liquidated.Job analysis ; Employment (Economic theory) ; Labor turnover

Turning 21: Life chances and uncertain transitions

  Traditionally, the transition from school to work has been important for young adults, and turning 21 was recognised as the marker of adulthood in Australia, when young people had jobs—and even families of their own. Social and economic changes over the past 30 years or so have made the transition from school to work more complex and less clear-cut. This report documents the factors that shape the lives of 123 young participants in the Life Chances Study, as they turn 21. Key points •    Stereotypes about young people obscure the diverse and complex lives of 21-year-olds. This diversity is shaped by family income, gender, ethnic background and resources. The 21-year-olds included university and TAFE students, full-time and part-time workers, young parents and jobseekers. Many were both studying and working. •    Those with fewer resources were more likely to identify as adults. They faced challenges that those with more resources could avoid. While some welcomed adulthood, others felt the burden of responsibilities. •    21-year-olds continued to rely on their families for advice, and emotional and financial support. The unequal access to resources reinforced inequalities because even though most had jobs, many still relied on their parents’ financial support—if they could. •    Disadvantage need not be intergenerational. Disadvantage or advantage persisted for some families, but not for all. Childhood in a low-income family did not necessarily condemn children to continuing disadvantage. •    Definitions of a ‘successful’ transition must take into account young people’s multiple activities and their wellbeing. Most 21-year-olds aspired to full-time employment. In this study, most of those who did not have a job and were not studying or in training had caring duties or mental health issues. Labelling these young people as ‘disengaged’ does not sufficiently capture their level of activity or wellbeing. •    Transitions for 21-year-olds are uncertain, but the social and economic resources needed to address this uncertainty are not evenly distributed. Those from high-income backgrounds with strong social supports had greater ‘choice’ while negotiating their pathways than those from lower income backgrounds. •    Policies need to address multidimensional disadvantage. The findings have implications for addressing socioeconomic inequalities as well as for targeted career and vocational guidance. Background The Life Chances Study is a unique longitudinal study initiated by the Brotherhood of St Laurence in 1990 to explore the impacts of family income and associated factors on children over time. It commenced as a study of 167 infants born in inner Melbourne and has followed the families as they have moved elsewhere. In stage 10 of the study we surveyed 123 young people and their parents to see how they were dealing with the important transitions towards adulthood. We also undertook 25 interviews to explore their situations in more depth