Economists analyzing a well-conducted randomized controlled trial or natural experiment and finding a statistically significant effect conclude that the null of no effect is unlikely to be true. But how frequently is this conclusion warranted? The answer depends on the proportion of tested nulls that are true and the test's power. I model the distribution of t-statistics in leading economics journals. Using my preferred model, 65% of narrowly rejected null hypotheses and 41% of all rejected null hypotheses with |t|<10 are likely to be false rejections. For the null to have only a .05 probability of being true requires a t of 5.48.

Prior to trade liberalization in the 1980s, New Zealand heavily protected low‐wage industries. Consequently, trade liberalization was desirable from the perspective of both traditional and new trade theories. While liberalization decreased employment in protected industries somewhat, it also significantly affected wages, noticeably diminishing the effect of liberalization on employment in previously protected industries and thus reducing the postliberalization shift in the industrial composition of employment. The small effect of liberalization on the composition of employment suggests that the effect of tariffs on wages and firms' monopoly power substantially eliminated any effect of protection on the distribution of employment.

Much nonmanagerial work is routine, with all workers having similar output most of the time. However, failure to address occasional challenges can be very costly, and consequently easily detected, while challenges handled well pass unnoticed. We analyze job assignment and worker monitoring for such “guardian” jobs. If monitoring costs are positive but small, monitoring is nonmonotonic in the firm’s belief about the probability that a worker is good. The model explains several empirical regularities regarding nonmanagerial internal labor markets: low use of performance pay, seniority pay, rare demotions, wage ceilings within grade, and wage jumps at promotion.

Using Italian Social Security records for male workers from a sample of firms in Turin from 1981 to 1983, we show that conditional on the worker's own wage the average wage in the establishment for similar workers is negatively related to quits. We also find that this variable predicts future wage growth. This is consistent with an economic model in which workers compare the longrun value of employment opportunities when making quit decisions.

The simplest economic theories of crime predict that profit-maximizing firms should follow strategies of minimal monitoring with large penalties for employee crime. We investigate possible reasons why firms actually spend considerable resources trying to detect employee malfeasance. We find that the most plausible explanations for firms' large outlays on monitoring of employees-legal restrictions on penalty clauses in contracts and the adverse impact of harsh punishment schemes on worker morale-are also consistent with the payment of premium (rent-generating) wages by cost-minimizing firms.