Efficiency of Thin and Thick Markets

In this paper, we propose a matching model to study the efficiency of thin and thick markets. Our model shows that the probabilities of matches in a thin market are significantly lower than those in a thick market. When applying our results to a job search model, it implies that, if the ratio of job candidates to job openings remains (roughly) a constant, the probability that a person can find a job is higher in a thick market than in a thin market. We apply our matching model to the U.S. academic market for new PhD economists. Consistent with the prediction of our model, a field of specialization with more job openings and more candidates has a higher probability of matching.

Initial Wage, Human Capital and Post Wage Differentials

Insufficiency in information with which firms judge the productivity of a worker for the first time in the market creates more randomness in initial wages than in later wages. This paper examines whether the initial randomness in wages may have a persistent effecton post wages. We set up a human capital accumulation in which an individual may respond to the positive error in initial wage by adjusting hours worked thereafter in her career, and consequently may receive higher future wages than those who draw a negative error in initial wages but otherwise are equivalent. The model predicts that the initial wage, in particular, its random component, is a persistently important factor having positive effecton future wages. Using data from the National Longitudinal Survey of Youth 79, we find empirical evidence that this effect is indeed positive and persists even after 20 years since the initial entry to labor market. The decomposition of initial wages by both parametric and nonparametric IV methods further shows that this effectis derived by the random component, nott he observable component, of the initial wage. It implies that the observed cross-sectional wage variation within group can be accounted for the initial randomness in wages.Human Capital Accumulation, Learning, Initial Wage, Wage Differentials

Three-dimensional magnetohydrodynamical simulations of the morphology of head-tail radio galaxies based on magnetic tower jet model

The distinctive morphology of head-tail radio galaxies reveals strong interactions between the radio jets and their intra-cluster environment, the general consensus on the morphology origin of head-tail sources is that radio jets are bent by violent intra-cluster weather. We demonstrate in this paper that such strong interactions provide a great opportunity to study the jet properties and also the dynamics of intra-cluster medium (ICM). By three-dimensional magnetohydrodynamical simulations, we analyse the detailed bending process of a magnetically dominated jet, based on the magnetic tower jet model. We use stratified atmospheres modulated by wind/shock to mimic the violent intra-cluster weather. Core sloshing is found to be inevitable during the wind-cluster core interaction, which induces significant shear motion and could finally drive ICM turbulence around the jet, making it difficult for jet to survive. We perform detailed comparison between the behaviour of pure hydrodynamical jets and magnetic tower jet, and find that the jet-lobe morphology could not survive against the violent disruption in all of our pure hydrodynamical jet models. On the other hand, the head-tail morphology is well reproduced by using a magnetic tower jet model bent by wind, in which hydrodynamical instabilities are naturally suppressed and the jet could always keep its integrity under the protection of its internal magnetic fields. Finally, we also check the possibility for jet bending by shock only. We find that shock could not bend jet significantly, so could not be expected to explain the observed long tails in head-tail radio galaxies.Comment: submitted to ApJ on December 9, 2016, and accepted on March 1st, 201