Examining the most heavily cited publications in labor economics from the early 1990s, I show that few of over 3,000 articles, citing them directly, replicates them. They are replicated more frequently using data from other time periods and economies, so that the validity of their central ideas has typically been verified. This pattern of scholarship suggests, beyond the currently required depositing of data and code upon publication, that there is little need for formal mechanisms for replication. The market for scholarship already produces replications of non-laboratory applied research.

The purpose of these letters is to help the individual obtain a job. When your commitment to the person is very weak, refuse to write rather than providing a letter that guarantees the subject a rejection. The decision is especially delicate when a colleague asks for a recommendation. In that case, agree to write, but end the letter by stating that you hope the colleague stays. (Even if you want the colleague to leave, anything less than admiration reduces the chance of achieving your mutual goal.) If the colleague is someone who has been denied tenure, refusing to write is particularly odious. In your letter:

There is a welter of advice about what topics to include, which audiovisual/computing wizardry to employ, and how to use modem learning theory in Microeconomics Principles classes (William Becker and Michael Watts, 1999). What appears lacking (except for Kenneth Elzinga, 2001) is plain advice aimed particularly at newer instructors on how to present material and treat students-generally how to avoid having the course burden students and instructor. The spur is my upset when people say economics was the most boring course in college and one they never understood. My only bona fides for providing this advice is experience, over 30 sections of Micro Principles with over 12,000 students. The advice is aimed toward instructors of sections of at least 100 students, but most applies in smaller sections as well. The crucial assumptions here are that students: (i) do not intend to take more economics; (ii) know very little about what economics is really about; and (iii) are very concerned about maintaining/raising their grade point averages. These assumptions regrettably characterize the majority of students in Micro Principles classes and should condition how we teach. They imply that the burden of teaching, including the sheer physical energy and attention required to demonstrate the relevance of economics and maintain students' interest, is greater than in other courses. They necessitate introducing only those techniques that will be used in class in analyzing real-world issues: Teach ideas, not techniques.' The purpose is to enable students to see economic principles in action in real life, not to prepare budding economics majors. I. In-Class Issues

This study examines the costs firms face in adjusting labor demand to exogenous shocks. Evidence on monthly plant-level data shows that adjustment proceeds in jumps: Employment is unchanged in response to small shocks, but moves instantaneously to a new equilibrium if the shocks are large. Results in the large literature that assumes smooth adjustment are due to aggregation of this nonlinear relation. The finding has implications for cyclical changes in productivity, for examining severance pay, layoff, and plant-closing restrictions, and all other policies that affect the cost of adjusting employment.

A major aspect of social policy in the United States during the 1960's was the effort to increase employment and lessen the extent of poverty. The effects of these efforts, in particular those of the Manpower Development and Training Act, have been discussed by economists solely within the framework of empirical cost-benefit analysis. In this note we take a different approach to the study of manpower programs. Under a set of admittedly restrictive assumptions we analyze the relative efficiencies in reducing unemployment of several alternative subsidy programs. It should be remembered that the reduction of unemployment is merely one goal of these programs and that the usefulness of our result must be qualified accordingly.