Comparison of fetal and maternal levels of immunglobulines indicate that the human placenta during pregnancy develops a specific transport mechanism for IgG. There are differences for the four subclasses with preferential transfer of IgG1 while the slowest transfer is seen for IgG2.

Using the December 1998 and August 2000 CPS Computer and Internet Supplements matched with subsequent CPS files, we ask which types of unemployed workers looked for work on line and whether Internet searchers became reemployed more quickly. In our data, Internet searchers have observed characteristics that are typically associated with shorter unemployment spells, and do spend less time unemployed. This unemployment differential is however eliminated and in some cases reversed when we hold observable characteristics constant. We conclude that either Internet job search is ineffective in reducing unemployment durations, or Internet job searchers are negatively selected on unobservables.

American business is devoting a growing share of resources to identifying and developing a worker characteristic called "leadership skill". Is there such a thing, and is it rewarded in labor markets? Using the Project Talent, NLS72 and High School and Beyond datasets, we show that men who occupied leadership positions in high school earn more as adults, even when cognitive skills are held constant. The pure leadership-wage effect varies, depending on definitions and time period, from four percent to twenty-four percent, and appears to have increased over time. High-school leaders are more likely to occupy managerial occupations as adults, and leadership skills command a higher wage premium within managerial occupations than in other jobs. We find evidence that leadership skill has a component that is determined before high school, but also find evidence suggesting that it is "teachable". * We thank the Institute for Social, Behavioral and Economic Research at UC Santa Barbara and the Spencer Foundation for research support. Simon Chapple, Dan Hamermesh, Christopher Jencks, Michael Ornstein, and James Rosenbaum provided helpful comments, as did seminar participants at University of British Columbia, the 2002 meetings of the

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. www.econstor.eu The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit organization supported by Deutsche Post Foundation. The center is associated with the University of Bonn and offers a stimulating research environment through its international network, workshops and conferences, data service, project support, research visits and doctoral program. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. Terms of use: Documents in D I S C U S S I O N P A P E R S E R I E SIZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be available directly from the author. While the Internet has been found to reduce trading frictions in a number of other markets, existing research has failed to detect such an effect in the labor market. In this paper, we replicate Kuhn and Skuterud's (2004) study -which found that Internet job search (IJS) was associated with longer unemployment durations in 1998/2000 -using comparable data from a decade later. We find that IJS now appears to be effective: it reduces individual workers' unemployment durations by about 25 percent. This finding is robust to controls for workers' AFQT scores and detailed indicators of Internet access. IJS appears to be most effective in reducing unemployment durations when used to contact friends and relatives, to send out resumes or fill out applications, and also to look at ads. We detect no effect of IJS on wage growth between jobs.JEL Classification: J64

Each week, the Dutch Postcode Lottery (PCL) randomly selects a postal code, and distributes cash and a new BMW to lottery participants in that code. We study the effects of these shocks on lottery winners and their neighbors. Consistent with the life-cycle hypothesis, the effects on winners' consumption are largely confined to cars and other durables. Consistent with the theory of in-kind transfers, the vast majority of BMW winners liquidate their BMWs. We do, however, detect substantial social effects of lottery winnings: PCL nonparticipants who live next door to winners have significantly higher levels of car consumption than other nonparticipants. JEL: D14, D91, H23, H27

We study explicit gender discrimination in a population of ads on a Chinese Internet job board. Gender-targeted job ads are common, favor women as often as men, and are much less common in jobs requiring higher levels of skill. Employers’ relative preferences for female versus male workers, on the other hand, are more strongly related to the preferred age, height, and beauty of the worker than to job skill levels. Almost two thirds of the variation in advertised gender preferences occurs within firms, and one third occurs within firm*occupation cells. Overall, these patterns are not well explained by a firm-level animus model, by a glass-ceiling model, or by models in which broad occupational categories are consistently gendered across firms. Instead, the patterns suggest a model in which firms have idiosyncratic preferences for particular job-gender matches, which are overridden in skilled positions by factors such as thinner labor markets or a greater incentive to search broadly for the most qualified candidate.

Manuscript prepared for Handbook of Labor Economics, volume 4, Orley Ashenfelter and David Card, editors. We thank Michael Kuhn and Loni Spilberg for excellent research assistance. We have done our utmost to identify as many lab experimental papers in labor economics as possible, and to represent the results of these papers accurately. Given the volume of recent research in this area and the deadline we have faced in writing this review, it is inevitable that we have missed some important work. We also sincerely hope that we have not mischaracterized any paper's conclusions. The authors apologize for these limitations in advance and nevertheless hope that our review provides a helpful guide to the 'lab labor' literature to date The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research. NBER working papers are circulated for discussion and comment purposes. They have not been peerreviewed or been subject to the review by the NBER Board of Directors that accompanies official NBER publications.

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit company supported by Deutsche Post World Net. The center is associated with the University of Bonn and offers a stimulating research environment through its research networks, research support, and visitors and doctoral programs. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. Terms of use: Documents in D I S C U S S I O N P A P E R S E R I E SIZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be available directly from the author. After declining for most of the century, the share of employed American men regularly working more than 50 hours per week began to increase around 1970. This trend has been especially pronounced among highly educated, high-wage, salaried, and older men. Using two decades of CPS data, we rule out a number of factors, including business cycles, changes in observed labor force characteristics, and changes in the level of men's real hourly earnings as primary explanations of this trend. Instead we argue that increases in salaried men's marginal incentives to supply hours beyond 40 accounted for the recent rise. Since these increases were accompanied by a rough constancy in real earnings at 40 hours, they can be interpreted as a compensated wage increase.JEL Classification: J22