The simplicity of the canonical search and matching model offers many advantages for the purpose of understanding the determinants and dynamics of unemployment. However, the spe cial assumption that a firm is composed of a sin gle worker and employer or that the production technology is linear is limiting. Lars A. Stole and Jeffrey Zwiebel (1996), Asher Wolinsky (2000), and Elhanan Helpman and Oleg Itskhoki (2008) generalize the original model to the case of many workers in a firm with a technology characterized by diminishing returns to labor. They find that all employers pay the same wage in steady state equi librium when only unemployed workers search. I extend their model by allowing for search on the job and show that a unique dispersed wage steady state equilibrium also exists with the prop erty that more productive employers pay more and are larger. Furthermore, inefficient characterizes the single wage equi librium, but employment is lower in the dispersed wage equilibrium because employers face stiffer competition. As a consequence, the dispersed wage equilibria can be more efficient. There is a close relationship between the equi libria of the search and matching model studied in this paper and those of the dynamic monopsony models of Peter A. Diamond (1971), Kenneth Burdett and Kenneth L. Judd (1983), and Burdett and Dale T. Mortensen (1998). The single wage equilibrium is the analogue of the Diamond equi librium while a dispersed wage equilibrium exists when employed workers search for essentially the same reason as in the Burdett-Mortensen model. Namely, there exists a nondegenerate interval of wages and a continuous distribution of vacancies over the interval such that the common

In a paper in the March 2004 AER, Justine Hastings concludes that the acquisition of an independent gasoline retailer, Thrifty, by a vertically integrated firm, ARCO, is associated with sizable price increases at competing stations. To better understand the mechanism to which she attributes this effect – which combines vertical integration and rebranding – we attempted but ultimately failed to reproduce the results using alternative data.

The Efficacy of Collaborative Learning Recitation Sessions on Student Outcomes by Kim P. Huynh, David T. Jacho-Chávez and James K. Self. Published in volume 100, issue 2, pages 287-91 of American Economic Review, May 2010

Several impatient investors with private costs C i face an indivisible irreversible investment opportunity whose value V is governed by geometric Brownian motion. The first investor i to seize the opportunity receives the entire payoff, V-C i . We characterize the symmetric Bayesian Nash equilibrium for this game. A laboratory experiment confirms the model's main qualitative predictions: competition drastically lowers the value at which investment occurs; usually the lowest-cost investor preempts the other investors; observed investment patterns in competition (unlike monopoly) are quite insensitive to changes in the Brownian parameters. Support is more qualified for the prediction that markups decline with cost.

Economywide Implications from US Bioenergy Expansion by Mark Gehlhar, Agapi Somwaru, Peter B. Dixon, Maureen T. Rimmer and Ashley R. Winston. Published in volume 100, issue 2, pages 172-77 of American Economic Review, May 2010

Can Mentoring Help Female Assistant Professors? Interim Results from a Randomized Trial by Francine D. Blau, Janet M. Currie, Rachel T. A. Croson and Donna K. Ginther. Published in volume 100, issue 2, pages 348-52 of American Economic Review, May 2010