Job separations, heterogeneity, and earnings inequality

Changes in the fraction of workers experiencing job separations can account for> most of the increase in earnings dispersion that occurred both between, as well as> within educational groups in the United States from the mid-1970s to the mid-> 1980s. This is not true of changes in average earnings losses following job separations.> A search model with exogenous human capital accumulation calibrated> to match some selected moments of the U.S. labor market is used to measure the> effects of changes in the fraction of workers experiencing job separations (extensive> margin) versus changes in average earnings losses following job separations> (intensive margin). While both margins do well in accounting for the increase in> the college premium, only the changes in the extensive margin do well in accounting> for the increases in the variance of both the permanent and transitory> components of earnings.Wages ; Income distribution

Photon emission in a constant magnetic field in 2+1 dimensional space-time

We calculate by the proper-time method the amplitude of the two-photon emission by a charged fermion in a constant magnetic field in (2+1)-dimensional space-time. The relevant dynamics reduces to that of a supesymmetric quantum-mechanical system with one bosonic and one fermionic degrees of freedom.Comment: 18 pages. v2: references added, some significant changes in the introductio

The Implications of Capital-Skill Complementarity in Economies with Large Informal Sectors

In most developing nations, formal workers tend to be more experienced and educated than informal workers, a fact often interpreted as evidence that low-skill workers face barriers to entry into the formal sector. Yet, there exists little direct evidence that labor markets are segmented in those nations. This paper describes a model where significant differences arise between workers across sectors even though labor markets are perfectly competitive. In equilibrium, the informal sector emphasizes low-skill work because informal managers have access to less outside financing, and choose to substitute low-skill labor for physical capital. We argue that subsidiary implications of the model for the organization of production are borne out by the existing evidence on informal economic activities in developing countries.

Finance matters

We present a model in which the importance of financial intermediation for development can be measured. We generate financial differences by varying the degree to which contracts can be enforced. Economies where enforcement is poor employ less capital and less efficient technologies. Yet, accounting for all the observed dispersion output requires a higher capital share or a lower elasticity of substitution between capital and labor than usually assumed. We find that the effects of changes in those technological parameters on output are markedly larger when financial frictions are present. Finance, that is, matters.Financial markets ; Productivity

Angiotensin II and VEGF are Involved in Angiogenesis Induced by Short-Term Exercise Training

Results from our laboratory have suggested a pathway involving angiotensin II type 1 (AT1) receptors and vascular endothelial growth factor (VEGF) in angiogenesis induced by electrical stimulation. The present study investigated if similar mechanisms underlie the angiogenesis induced by short-term exercise training. Seven days before training and throughout the training period, male Sprague-Dawley rats received either captopril or losartan in their drinking water. Rats underwent a 3-day treadmill training protocol. The tibialis anterior and gastrocnemius muscles were harvested under anesthesia and lightly fixed in formalin (vessel density) or frozen in liquid nitrogen (VEGF expression). In controls, treadmill training resulted in a significant increase in vessel density in all muscles studied. However, the angiogenesis induced by exercise was completely blocked by either losartan or captopril. Western blot analysis showed that VEGF expression was increased in the exercised control group, and both losartan and captopril blocked this increase. The role of VEGF was directly confirmed using a VEGF-neutralizing antibody. These results confirm the role of angiotensin II and VEGF in angiogenesis induced by exercise

A multi-sectoral approach to the U.S. Great Depression

We document sectoral differences in changes in output, hours worked, prices, and nominal wages in the United States during the Great Depression. We explore whether contractionary monetary shocks combined with different degrees of nominal wage frictions across sectors are consistent with both sectoral as well as aggregate facts. To do so, we construct a two-sector model where goods from each sector are used as intermediates to produce the sectoral goods that in turn produce final output. One sector is assumed to have flexible nominal wages, while nominal wages in the other sector are set using Taylor contracts. We calibrate the model to the U.S. economy in 1929, and then feed in monetary shocks estimated from the data. We find that while the model can qualitatively replicate the key sectoral facts, it can account for less than a third of the decline in aggregate output. This decline in output is roughly half as large as the one implied by a one-sector model. Alternatively, if wages are set using Calvo-type contracts, the decline in output is even smaller.Depressions ; Wages ; Prices