2024 Ephraim Lecture: Megan T. Stevenson

What Randomized Controlled Trials Teach Us about the Structure of the Social World

Social scientists have been conducting randomized controlled trials (RCTs) to evaluate the impact of various policies and programs for more than 50 years. The goal is to identify "what works" in order to engineer improvements in the social world. In the inaugural Ephraim Lecture, Stevenson will discuss implications of a mostly-unknown fact: most interventions evaluated by RCTs are shown to have little lasting effect, and the rare instances of success tend not to replicate in other times and places. While this might be disappointing from the perspective of someone hoping to learn what levers to pull to achieve change, she will argue that this teaches us something valuable about the structure of the social world.

When it comes to the type of limited-scope interventions that lend themselves to high-quality impact evaluation, social change is hard to engineer. Stabilizing forces push people back toward the path they would have been on absent the intervention. Cascades—small interventions that lead to large and lasting changes—are rare. And causal processes are complex and context-dependent, meaning that success achieved in one setting may not port well to another. This has a variety of implications. It suggests that a dominant perspective on social change—one that forms a pervasive background for academic research and policymaking—is at least partially a myth. Understanding this shifts how we should think about social change and raises important questions about the process of knowledge generation.

Megan T. Stevenson is the Henry L. and Grace Doherty Charitable Foundation Professor of Law and Professor of Economics at University of Virginia.

This Donald M. Ephraim, ’55, Prize Lecture was delivered on October 15, 2024.