Must Watch Propaganda: The Marginal Treatment Effect of Foreign Media among Always-Takers

Abstract

Studies of political persuasion often use an exogenous encouragement as an instrument for persuasive messaging. However, for some people, such encouragement is insufficient, while for others it is unnecessary. These individuals are excluded from methods that only estimate a treatment effect among compliers. Our paper provides identification results for the average treatment effects of non-compliers using the marginal treatment effect framework. With these tools we extend research finding that exposure to West German television increases support for communism. We find that, because of self-selection, for those who watch West German TV regardless of signal quality, i.e. always-takers, cutting off West German television would have increased support for communism. Our extrapolation shows that media choices reinforce, rather than mollify, political preferences.

Keywords: Political persuasion, instrumental variable, non-compliance, marginal treatment effect, linear programming, partial identification