Worker Flows, Job Flows and Unemployment in a Matching Model

Standard matching models of unemployment assume that workers and job flows are identical. This is in stark contrast to empirical evidence that job flows in fact only account for a fraction of worker ßows, that unemployment exits only account for a fraction of hires and that these fractions vary over the cycle. In this paper, we develop and calibrate a model based on the Mortensen and Pissarides approach but that emphasises this issue. We show that this matters - that it has very different implications for our view of unemployment dynamics. The key features of our model relate to the search options of the worker, and the job creation decision by firms. We allow workers to search whilst employed, and firms to re-advertise jobs that have been quit from. This leads us to use a different job creation process, whereby potential vacancies, or job 'ideas', arise at a finite rate per period over a range of idiosyncratic productivities. In the standard setting, there is an unlimited supply of potential vacancies at the top idiosyncratic productivity. The main results are as follows. First, the presence of on-the-job search has a substantial impact on labour market equilibrium, whereby equilibrium unemployment is lower and exhibits a higher turnover rate. On-the-job search renders the unemployment inflow rate more sensitive to the cycle: in all cases, the inflow rate is found to be more cyclically sensitive than the outflow rate, suggesting that most unemployment dynamics occur through this channel. This confrms empirical results for Great Britain (Burgess and Turon (2005)). Second, our model offers some insight into a (two-way) relationship between job-to-job flows, which drives the difference between worker and job flows, and the extent of wage dispersion. More wage dispersion increases the incentive to search on-the-job and more on-the-job search widens the range of viable productivities and leads to lower wages at the bottom of the wage distribution, thereby increasing wage dispersion. Third, changes in the model's exogenous parameters impact unemployment to a considerable degree by changing the level of employed job search.Unemployment, on-the-job search, worker flows, job flows, matching.

Unemployment equilibrium and on-the-job search

This paper uses the search and matching framework to explore the impact of employed job search on the labour market. We allow for endogenous employed job search, endogenous job destruction and heterogenous job creation. Job flows and workers flows do not coincide as we allow for job-to-job flows, firms' churning of workers and labour force entries and exits. Employed job search is shown to have a substantial impact on unemployment dynamics but a negligible one on the level of unemployment. It also plays a key role in propagating a shock to institutions or to the economy to the labour market.unemployment, on-the-job search, job destruction, business cycles, matching

The Cyclical Behavior of Equilibrium Unemployment and Vacancies – A Comment

The Mortensen-Pissarides model is an attractive model because it is tractable, delivers some intuitive comparative statics and permits policy analysis. However, Shimer (2005) shows that the model generates far too little volatility in its key variables - unemployment and vacancies - relative to the variation in the shock variables. Shimer identifes the flexibility of wages as the key issue. In this Comment, we show that it is possible to generate suffcient volatility in unemployment and vacancies whilst retaining the standard wage determination process. We set out a model with two important changes from the Mortensen-Pissarides approach: job search by the employed is allowed, and the vacancy creation condition is changed to allow churning of workers. Calibrating the model to UK data, we show that our model can produce volatility in the unemployment and vacancy series to match the data; we confirm for the UK that the Mortensen-Pissarides model cannot, as shown by Shimer for the US.Unemployment, on-the-job search, worker flows, job flows, matching.

Dynamic current susceptibility as a probe of Majorana bound states in nanowire-based Josephson junctions

We theoretically study a Josephson junction based on a semiconducting nanowire subject to a time-dependent flux bias. We establish a general density matrix approach for the dynamical response of the Majorana junction and calculate the resulting flux-dependent susceptibility using both microscopic and effective low-energy descriptions for the nanowire. We find that the diagonal component of the susceptibility, associated with the dynamics of the Majorana states populations, dominates over the standard Kubo contribution for a wide range of experimentally relevant parameters. The diagonal term, thus far unexplored in the context of Majorana physics, allows to probe accurately the presence of Majorana bound states in the junction.Comment: 5 pages, 3 figures, 15 pages of supplemental materia

Restorative Survey of a Human Osteological Teaching Collection: Mitigating Objectification and Structural Violence After Death

Interdisciplinary discussions considering the impacts of dubious acquisition and management of human skeletal collections have identified these assemblages as venues for perpetuating structural violence after death. Lack of provenance across many large and small “legacy” skeletal collections prevents clear solutions for treatment of individuals who cannot be clearly associated with descendant communities or identified as donors. A critical examination of our department’s collection and classroom presentation practices as they pertain to the individuals in the Human Osteological Teaching Collection (HOTC) serves to mitigate this violence and restore a degree of personhood to the individuals who contribute to generations of education. The individuals (n=6) were assessed for presence and preservation of individual skeletal elements; osteometric data was then collected according to methodological standards. Each individual was morphologically evaluated to generate estimations for phenotypic sex and skeletal age. Finally, visual assessments of pathological lesions and taphonomy were conducted on a presence/absence basis and noted in the inventory forms. Morphological ancestry or “racial” estimations were excluded from this study, as they are rooted in and perpetuate the false idea of race as a biological phenomenon. Our results reflect a typical profile across the HOTC individuals: middle- to olderadult (35-50+) males, displaying one or more pathological lesion and one or more instance of postmortem skeletal damage. These results reflect the issues of objectification and structural violence identified across other osteological collections and highlight the importance of presenting skeletal teaching collections with a focus on care and ethical treatment of marginalized individuals

A Resolved Simulation Approach to Investigate the Separation Behavior in Solid Bowl Centrifuges Using Material Functions

The separation of finely dispersed particles from liquids is a basic operation in mechanical process engineering. On an industrial scale, continuously operating decanter centrifuges are often used, whose separation principle is based on the density difference between the solid and the liquid phase due to high g-forces acting on both phases. The design of centrifuges is based on the experience on the individual manufacturer or simplified black box models, which only consider a stationary state. Neither the physical behavior of the separation process nor the sediment formation and its transport is considered. In this work, a computationally-efficient approach is proposed to simulate the separation process in decanter centrifuges. Thereby, the open-source computation software OpenFOAM was used to simulate the multiphase flow within the centrifuge. Sedimentation, consolidation of the sediment, and its transport are described by material functions which are derived from experiments. The interactions between the particles and the fluid are considered by locally defined viscosity functions. This work shows that the simulation method is suitable for describing the solid-liquid separation in a simplified test geometry of a decanter centrifuge. In addition, the influence of the rheological behavior on the flow in the test geometry can be observed for the first time

Association of Cumulative Lead Exposure with Parkinson's Disease

BACKGROUND. Research using reconstructed exposure histories has suggested an association between heavy metal exposures, including lead, and Parkinson's disease (PD), but the only study that used bone lead, a biomarker of cumulative lead exposure, found a nonsignificant increase in risk of PD with increasing bone lead. OBJECTIVES. We sought to assess the association between bone lead and PD. METHODS. Bone lead concentrations were measured using 109Cd excited K-shell X-ray fluorescence from 330 PD patients (216 men, 114 women) and 308 controls (172 men, 136 women) recruited from four clinics for movement disorders and general-community cohorts. Adjusted odds ratios (ORs) for PD were calculated using logistic regression. RESULTS. The average age of cases and controls at bone lead measurement was 67 (SD = 10) and 69 (SD = 9) years of age, respectively. In primary analyses of cases and controls recruited from the same groups, compared with the lowest quartile of tibia lead, the OR for PD in the highest quartile was 3.21 [95% confidence interval (CI), 1.17-8.83]. Results were similar but slightly weaker in analyses restricted to cases and controls recruited from the movement disorders clinics only (fourth-quartile OR = 2.57; 95% CI, 1.11-5.93) or when we included controls recruited from sites that did not also contribute cases (fourth-quartile OR = 1.91; 95% CI, 1.01-3.60). We found no association with patella bone lead. CONCLUSIONS. These findings, using an objective biological marker of cumulative lead exposure among typical PD patients seen in our movement disorders clinics, strengthen the evidence that cumulative exposure to lead increases the risk of PD.National Institutes of Health (R01-ES010798, K01-ES01265

institutional innovation from the bottom up?

A sustainable economy fulfills societal needs in a fundamentally different way to the current economic system. Improvements to the efficiency of existing technologies or practices appear insufficient for achieving sustainable development within the planetary boundaries. Disruptive, systemic and transformational changes appear necessary in order to replace existing technologies and practices to establish a sustainable economy. Such innovations often start out in niches; however, the scaling up and the ultimate replacement of current socio-technical systems requires governance to allow for the coordination of actors, the reorganization of socio-technical systems and the mobilization and allocation of resources. As governmental institutions are part of the current (non-sustainable) systems and thereby fail to provide coherent, integrated and transformative governance, we explore whether institutional innovation from non-state actors can step in to provide governance of transformation processes. Based on explorative qualitative case studies of networks in the food sector, city planning and reporting tools, we analyze the potential of bottom-up institutional innovations to coordinate actors in transformation processes