A Binary IV Model for Persuasion: Profiling Persuasion Types among Compliers

• In Event: Methodological Advances in Causal Inference

Abstract

In the empirical study of persuasion, researchers often use a binary instrument to encourage individuals to consume information and take some action. Under the Imbens-Angrist instrumental variable model assumptions, the binary IV model can recover the proportion of people who take the action under the treatment and control conditions. I show that with the monotone treatment response assumption, it is possible to identify the joint distributions of potential outcomes among compliers. This is necessary to identify the percentage of persuadable individuals and their statistical characteristics. Specifically, I develop a weighting method that helps researchers identify the statistical characteristics of persuasion types: compliers and always-persuaded, compliers and persuaded, and compliers and never-persuaded. These findings extend the ”Kappa weighting” results in Abadie (2003). I also provide a sharp test on the two sets of identification assumptions. The test boils down to testing whether there exists a nonnegative solution to a possibly under-determined system of linear equations with known coefficients. I also develop a simple sensitivity analysis to assess the sensitivity of the results with respect to the monotone treatment response assumption. An application based on Green et al. (2003) is provided. The result shows that among compliers, roughly 10% voters are persuadable. The results are consistent with the findings that voters’ voting behaviors are highly persistent.

Author

• Arthur Zeyang Yu, University of Chicago