Union Threat Effects and Nonunion Industry Wage Differentials

We investigate the impact of union strength on changes in nonunion wages and employment. The prevailing model in this area is the threat model, which predicts that increases in union strength cause increases in nonunion wages and decreases in nonunion employment. In testing the threat model, we are also testing two alternatives, the crowding and complements models. In contrast to the prediction of the threat model, decreases in the percent organized (reflecting a declining union threat) are associated with increases in the nonunion wage. Furthermore, increases in union wages appear to decrease, rather than to increase, nonunion wages. Evidence on the determinants of intra-industry variation in nonunion wage premia is somewhat more consistent with the crowding model and is strikingly consistent with the complements model of union and nonunion wage determination. Further evidence on the determinants of intra-industry variation in nonunion employment is consistent with the complements model and the threat model; movements in nonunion industry employment are negatively related to changes in proxies for union strength. Thus, the combined evidence supports the complements model, but neither the threat model nor the crowding model.

Postponement and recuperation of Belgian fertility: how are they related to rising female educational attainment?

Fertility trends in Europe after 1970 are routinely referred to in terms of the postponement of fertility. The shortening of the effective reproductive lifespan and its association with post-materialist values have raised questions as to whether fertility can or will be recuperated. Decomposition of cohort fertility in Belgium by level of education shows that the postponement of fertility after 1970 is closely related to the expansion of education: compared with cohorts born in 1946-1950, 40 to 50 per cent of the difference in cumulated fertility at age 25 in the 1951-1975 birth cohorts is attributable to rising educational levels. Educational differentials also prove relevant with regard to the recuperation of fertility at older ages as the tempo and quantum of order-specific fertility have responded differently to variations in the economic and policy context, depending on the educational level considered. Differential fertility trends by level of education have thus attenuated the relationship between female educational attainment and completed fertility in recent cohorts.

A generalized model of mutation-selection balance with applications to aging

A probability model is presented for the dynamics of mutation-selection balance in a haploid infinite-population infinite-sites setting sufficiently general to cover mutation-driven changes in full age-specific demographic schedules. The model accommodates epistatic as well as additive selective costs. Closed form characterizations are obtained for solutions in finite time, along with proofs of convergence to stationary distributions and a proof of the uniqueness of solutions in a restricted case. Examples are given of applications to the biodemography of aging, including instabilities in current formulations of mutation accumulation.Comment: 20 pages Updated to include more historical comment and references to the literature, as well as to make clear how our non-linear, non-Markovian model differs from previous linear, Markovian particle system and measure-valued diffusion models. Further updated to take into account referee's comment

The Age-Specific Force of Natural Selection and Walls of Death

W. D. Hamilton's celebrated formula for the age-specific force of natural selection furnishes predictions for senescent mortality due to mutation accumulation, at the price of reliance on a linear approximation. Applying to Hamilton's setting the full non-linear demographic model for mutation accumulation of Evans et al. (2007), we find surprising differences. Non-linear interactions cause the collapse of Hamilton-style predictions in the most commonly studied case, refine predictions in other cases, and allow Walls of Death at ages before the end of reproduction. Haldane's Principle for genetic load has an exact but unfamiliar generalization.Comment: 27 page

The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf Catalog

We have compiled photometric data from the Wide-field Infrared Survey Explorer All Sky Survey and other archival sources for the more than 2200 objects in the original McCook & Sion Catalog of Spectroscopically Identified White Dwarfs. We applied color-selection criteria to identify 28 targets whose infrared spectral energy distributions depart from the expectation for the white dwarf photosphere alone. Seven of these are previously known white dwarfs with circumstellar dust disks, five are known central stars of planetary nebulae, and six were excluded for being known binaries or having possible contamination of their infrared photometry. We fit white dwarf models to the spectral energy distributions of the remaining ten targets, and find seven new candidates with infrared excess suggesting the presence of a circumstellar dust disk. We compare the model dust disk properties for these new candidates with a comprehensive compilation of previously published parameters for known white dwarfs with dust disks. It is possible that the current census of white dwarfs with dust disks that produce an excess detectable at K-band and shorter wavelengths is close to complete for the entire sample of known WDs to the detection limits of existing near-IR all-sky surveys. The white dwarf dust disk candidates now being found using longer wavelength infrared data are drawn from a previously underrepresented region of parameter space, in which the dust disks are overall cooler, narrower in radial extent, and/or contain fewer emitting grains.Comment: accepted for publication in The Astrophysical Journal; 34 pages, 5 figures, 5 tables; added missing reference in Section 2 (p. 7

Monitoring LMXBs with the Faulkes Telescopes

We have been undertaking a monitoring project of 13 low-mass X-ray binaries (LMXBs) using FT North since early 2006. The introduction of FT South has allowed us to extend this monitoring to include 15 southern hemisphere LMXBs. With new instrumentation, we also intend to expand this monitoring to include both infrared wavelengths and spectroscopy.Comment: Conference proceedings from 'A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environments', 28 Oct - 2 Nov, St. Petersburg Beach, FL. 3 pages, 3 figure