What Can We Learn from Experiments? Understanding the Threats to the Scalability of Experimental Results
梳理了小型实验效果在推广到大规模时效果缩水的主要原因，帮助政策制定者和研究者理解可扩展性失效的机制，从而设计更可靠的干预方案。
Policymakers often consider interventions at the scale of the population, or some other large scale. One of the sources of information about the potential effects of such interventions is experimental studies conducted at a significantly smaller scale. A common occurrence is for the treatment effects detected in these small-scale studies to diminish substantially in size when applied at the larger scale that is of interest to policymakers. This paper provides an overview of the main reasons for a breakdown in scalability. Understanding the principal mechanisms represents a first step toward formulating countermeasures that promote scalability.