Help-Wanted Advertising, Job Vacancies, and Unemployment

macroeconomics, unemployment

Flexible Staffing Arrangements and Employers' Short-Term Adjustment Strategies

This paper reports new evidence from a survey of over 408 U.S. employers concerning their use of temporary and on-call workers. More than 90 percent of responding organizations reported reliance on these flexible staffing arrangements. They accounted for an average of 1.5 percent of total labor input at user organizations during 1985; at some organizations, they accounted for 10 percent or even 20 percent of total labor input. Four-fifths of survey respondents indicated that flexible staffing arrangements play an important role in absorbing workload fluctuations. Moreover, organizations with highly seasonal or highly cyclical demand made significantly greater use of flexible staffing arrangements during 1985 than organizations with less seasonal or less cyclical demand. The use of flexible staffing arrangements appears to be a more important component of employers' short-term adjustment strategies than has previously been recognized.

The Visibility of Galactic Bars and Spiral Structure At High Redshifts

We investigate the visibility of galactic bars and spiral structure in the distant Universe by artificially redshifting 101 B-band CCD images of local spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. Our artificially redshifted images correspond to Hubble Space Telescope I-band observations of the local galaxy sample seen at z=0.7, with integration times matching those of both the very deep Northern Hubble Deep Field data, and the much shallower Flanking Field observations. The expected visibility of galactic bars is probed in two ways: (1) using traditional visual classification, and (2) by charting the changing shape of the galaxy distribution in "Hubble space", a quantitative two-parameter description of galactic structure that maps closely on to Hubble's original tuning fork. Both analyses suggest that over 2/3 of strongly barred luminous local spirals i.e. objects classified as SB in the Third Reference Catalog) would still be classified as strongly barred at z=0.7 in the Hubble Deep Field data. Under the same conditions, most weakly barred spirals (classified SAB in the Third Reference Catalog) would be classified as regular spirals. The corresponding visibility of spiral structure is assessed visually, by comparing luminosity classifications for the artificially redshifted sample with the corresponding luminosity classifications from the Revised Shapley Ames Catalog. We find that for exposures times similar to that of the Hubble Deep Field spiral structure should be detectable in most luminous low-inclination spiral galaxies at z=0.7 in which it is present. [ABRIDGED]Comment: Accepted for publication in The Astronomical Journa

Changes in Unemployment Duration and Labor Force Attachment

This paper accounts for the observed increase in unemployment duration relative to the unemployment rate in the U.S. over the past thirty years, typified by the record low level of short-term unemployment. We show that part of the increase is due to changes in how duration is measured, a consequence of the 1994 Current Population Survey redesign. Another part is due to the passage of the baby boomers into their prime working years. After accounting for these shifts, most of the remaining increase in unemployment duration relative to the unemployment rate is concentrated among women, whose unemployment rate has fallen sharply in the last two decades while their unemployment duration has increased. Using labor market transition data, we show that this is a consequence of the increase in women's labor force attachment.

Effective Screening due to Minihalos During the Epoch of Reionization

We show that the gaseous halos of collapsed objects introduce a substantial cumulative opacity to ionizing radiation, even after the smoothly distributed hydrogen in the intergalactic medium has been fully reionized. This opacity causes a delay of around unity in redshift between the time of the overlap of ionized bubbles in the intergalactic medium and the lifting of complete Gunn-Peterson Lyman alpha absorption. The minihalos responsible for this screening effect are not resolved by existing numerical simulations of reionization.Comment: 24 pages, 5 figures, submitted to Ap