Three Essays on Skill Heterogeneity in Frictional Labor Markets

This dissertation is composed of three essays using labor search models to explore the role of skill mismatch in the labor market. The first, “Skill Mismatch in Frictional Labor Markets”, provides theory and evidence on pair-specific skill mismatch in the labor market, defined as the gap between an individual’s skills and the requirements of her job. Employment data from the NLSY97 display some degree of positive sorting into occupations on the basis of cognitive skills, but skill mismatch is pervasive and costly. I develop and estimate a labor search model featuring heterogeneity in worker skills and firm skill requirements that demonstrates how search frictions induce voluntary mismatch acceptance. In addition, the model indicates that skill mismatch is countercyclical; as the labor market tightens, mismatch tolerance falls and wages rise for all workers. However, the elasticity of mismatch tolerance with respect to market tightness varies systematically across the skill space, leading to changes in the composition of employment over the business cycle. While the model generates levels of mismatch broadly consistent with the data, the degree of positive sorting is underestimated for higher-skilled workers. The second chapter, “Targeted Search in Heterogeneous Labor Markets”, extends the theory of targeted search by introducing continuous skill heterogeneity among workers and firms in frictional labor markets. Workers are unable to fully direct their search, but instead pay an information cost to reduce the variance of the job offer distribution. A lower variance increases the worker’s expected match quality but decreases the offer arrival rate. Results show higher-skilled workers target their search more intensely, decreasing the expected level of mismatch among higher-skilled workers and allowing the model to better fit the data on skill mismatch and sorting. The third chapter, “Skill Mismatch and the Equilibrium Distribution of Vacancies”, builds on the model in the first chapter by endogenizing the skill distribution of vacancies. The model generates an equilibrium distribution of vacancies in the skill space that depends on labor market conditions such as bargaining power, matching efficiency, and the distribution of unemployed workers. Job creation depends critically on mismatch tolerance: higher levels of expected mismatch reduce the expected value of a vacancy. The model provides new predictions on the response of job creation to the skill distribution of unemployed workers, which can be tested using data on job postings by occupation

Severity of Visual Field Loss at First Presentation to Glaucoma Clinics in England and Tanzania

Purpose: To compare severity of visual field (VF) loss at first presentation in glaucoma clinics in England and Tanzania. Methods: Large archives of VF records from automated perimetry were used to retrospectively examine vision loss at first presentation in glaucoma clinics in Tanzania (N = 1,502) and England (N = 9,264). Mean deviation (MD) of the worse eye at the first hospital visit was used as an estimate of detectable VF loss severity. Results: In Tanzania, 44.7% {CI95%: 42.2, 47.2} of patients presented with severe VF loss (< −20 dB), versus 4.6% {4.1, 5.0} in England. If we consider late presentation to also include cases of advanced loss (-12.01 dB to -20 dB), then the proportion of patients presenting late was 58.1% {55.6, 60.6} and 14.0% {13.3, 14.7}, respectively. The proportion of late presentations was greater in Tanzania at all ages, but the difference was particularly pronounced among working-age adults, with 50.3% {46.9, 53.7} of 18–65-year-olds presenting with advanced or severe VF loss, versus 10.2% {9.3, 11.3} in England. In both countries, men were more likely to present late than women. Conclusions: Late presentation of glaucoma is a problem in England, and an even greater challenge in Tanzania. Possible solutions are discussed, including increased community eye-care, and a more proactive approach to case finding through the use of disruptive new technologies, such as low-cost, portable diagnostic aids

Number of People Blind or Visually Impaired by Glaucoma Worldwide and in World Regions 1990 – 2010: A Meta-Analysis

Objective: To assess the number of individuals visually impaired or blind due to glaucoma and to examine regional differences and temporal changes in this parameter for the period from 1990 to 2012. Methods: As part of the Global Burden of Diseases (GBD) Study 2010, we performed a systematic literature review for the period from 1980 to 2012. We primarily identified 14,908 relevant manuscripts, out of which 243 high-quality, population-based studies remained after review by an expert panel that involved application of selection criteria that dwelt on population representativeness and clarity of visual acuity methods used. Sixty-six specified the proportion attributable to glaucoma. The software tool DisMod-MR (Disease Modeling–Metaregression) of the GBD was used to calculate fraction of vision impairment due to glaucoma. Results: In 2010, 2.1 million (95% Uncertainty Interval (UI):1.9,2.6) people were blind, and 4.2 (95% UI:3.7,5.8) million were visually impaired due to glaucoma. Glaucoma caused worldwide 6.6% (95% UI:5.9,7.9) of all blindness in 2010 and 2.2% (95% UI:2.0,2.8) of all moderate and severe visual impairment (MSVI). These figures were lower in regions with younger populations (10%). From 1990 to 2010, the number of blind or visually impaired due to glaucoma increased by 0.8 million (95%UI:0.7, 1.1) or 62% and by 2.3 million (95%UI:2.1,3.5) or 83%, respectively. Percentage of global blindness caused by glaucoma increased between 1990 and 2010 from 4.4% (4.0,5.1) to 6.6%. Age-standardized prevalence of glaucoma related blindness and MSVI did not differ markedly between world regions nor between women. Significance: By 2010, one out of 15 blind people was blind due to glaucoma, and one of 45 visually impaired people was visually impaired, highlighting the increasing global burden of glaucoma

Intersection of inflammation and herbal medicine in the treatment of osteoarthritis

Herbal remedies and dietary supplements have become an important area of research and clinical practice in orthopaedics and rheumatology. Understanding the risks and benefits of using herbal medicines in the treatment of arthritis, rheumatic diseases, and musculoskeletal complaints is a key priority of physicians and their patients. This review discusses the latest advances in the use of herbal medicines for treating osteoarthritis (OA) by focusing on the most significant trends and developments. This paper sets the scene by providing a brief introduction to ethnopharmacology, Ayurvedic medicine, and nutrigenomics before discussing the scientific and mechanistic rationale for targeting inflammatory signalling pathways in OA by use of herbal medicines. Special attention is drawn to the conceptual and practical difficulties associated with translating data from in-vitro experiments to in-vivo studies. Issues relating to the low bioavailability of active ingredients in herbal medicines are discussed, as also is the need for large-scale, randomized clinical trial

Sports Participation and Juvenile Delinquency: A Meta-Analytic Review

Participation in sports activities is very popular among adolescents, and is frequently encouraged among youth. Many psychosocial health benefits in youth are attributed to sports participation, but to what extent this positive influence holds for juvenile delinquency is still not clear on both the theoretical and empirical level. There is much controversy on whether sports participation should be perceived as a protective or a risk factor for the development of juvenile delinquency. A multilevel meta-analysis of 51 published and unpublished studies, with 48 independent samples containing 431 effect sizes and N = 132,366 adolescents, was conducted to examine the relationship between sports participation and juvenile delinquency and possible moderating factors of this association. The results showed that there is no overall significant association between sports participation and juvenile delinquency, indicating that adolescent athletes are neither more nor less delinquent than non-athletes. Some study, sample and sports characteristics significantly moderated the relationship between sports participation and juvenile delinquency. However, this moderating influence was modest. Implications for theory and practice concerning the use of sports to prevent juvenile delinquency are discussed. Keywords Sports participation Juvenile delinquency Multilevel meta-analysis Revie

Three Essays on Skill Heterogeneity in Frictional Labor Markets

This dissertation is composed of three essays using labor search models to explore the role of skill mismatch in the labor market. The first, Skill Mismatch in Frictional Labor Markets , provides theory and evidence on pair-specific skill mismatch in the labor market, defined as the gap between an individual\u27s skills and the requirements of her job. Employment data from the NLSY97 display some degree of positive sorting into occupations on the basis of cognitive skills, but skill mismatch is pervasive and costly. I develop and estimate a labor search model featuring heterogeneity in worker skills and firm skill requirements that demonstrates how search frictions induce voluntary mismatch acceptance. In addition, the model indicates that skill mismatch is countercyclical; as the labor market tightens, mismatch tolerance falls and wages rise for all workers. However, the elasticity of mismatch tolerance with respect to market tightness varies systematically across the skill space, leading to changes in the composition of employment over the business cycle. While the model generates levels of mismatch broadly consistent with the data, the degree of positive sorting is underestimated for higher-skilled workers. The second chapter, Targeted Search in Heterogeneous Labor Markets\u27\u27, extends the theory of targeted search by introducing continuous skill heterogeneity among workers and firms in frictional labor markets. Workers are unable to fully direct their search, but instead pay an information cost to reduce the variance of the job offer distribution. A lower variance increases the worker\u27s expected match quality but decreases the offer arrival rate. Results show higher-skilled workers target their search more intensely, decreasing the expected level of mismatch among higher-skilled workers and allowing the model to better fit the data on skill mismatch and sorting. The third chapter, Skill Mismatch and the Equilibrium Distribution of Vacancies\u27\u27, builds on the model in the first chapter by endogenizing the skill distribution of vacancies. The model generates an equilibrium distribution of vacancies in the skill space that depends on labor market conditions such as bargaining power, matching efficiency, and the distribution of unemployed workers. Job creation depends critically on mismatch tolerance: higher levels of expected mismatch reduce the expected value of a vacancy. The model provides new predictions on the response of job creation to the skill distribution of unemployed workers, which can be tested using data on job postings by occupation

Three-dimensional high-density co-culture with primary tenocytes induces tenogenic differentiation in mesenchymal stem cells

Mesenchymal stem cells (MSCs) have potential applications in regenerative medicine and tissue engineering and may represent an attractive option for tendon repair and regeneration. Thus far the ability of MSCs to differentiate into tenocytes in vitro has not been investigated. Experiments were performed with and without growth factors (IGF-1, TGF-β1, IGF-1/TGF-β1, PDGF-BB, and BMP-12), in co-cultures of tenocytes and MSCs mixed in different ratios and by culturing MSCs with spent media obtained from primary tenocytes. Tenogenesis was induced in MSCs through a combination of treatment with IGF-1 and TGF-β1, in high-density co-cultures and through cultivation with the spent media from primary tenocytes. Electron microscopy and immunoblotting were used to demonstrate up-regulation of collagen I/III, decorin, tenomodulin, β1-Integrin, MAPKinase pathway (Shc, Erk1/2), and scleraxis in the co-cultures and provide simultaneous evidence for the inhibition of apoptosis. In monolayer co-cultures extensive intercellular contacts between MSCs and tenocytes were observed. Cells actively exchanged vesicles, which were labeled by using immunofluorescence and immunogold techniques, suggesting the uptake and interchange of soluble factors produced by the MSCs and/or tenocytes. We conclude that MSCs possess tenogenic differentiation potential when provided with relevant stimuli and a suitable microenvironment. This approach may prove to be of practical benefit in future tissue engineering and tendon regenerative medicine research