The Diffusion of Policy Perceptions: Evidence from a Structural Topic Model∗ Fabrizio Gilardi† Charles R. Shipan‡ Bruno Wueest§ June 22, 2015 Abstract Policy diffusion means that policies in one unit (such as states, cantons, and cities) are influenced by policies in other units. The literature has established convincingly that diffusion is an important determinant of policy choices, but the same process can also shape how policies are perceived, both before and after they are adopted, if they are adopted at all. This paper studies this process in the case of smoking bans in U.S. states. It relies on an original dataset of over 370,000 articles published in sixteen American newspapers between 1996 and 2014 and uses structural topic models to estimate how smoking bans have been perceived and how perceptions changes as a function of policy adoption in nearby states. The preliminary results show how the structural topic model can be used to study the diffusion of policy perceptions. ∗We thank Katrin Affolter, Nina Buddeke, Sarah Däscher, Jeremy Gelman, Andrea Häuptli, Geoff Lorenz, Adriano Meyer, Christian Müller, and Thomas Willi for excellent research assistance, Klaus Rotherhäusler for his help with the implementation of the computational linguistic methods, and Jude Hays for helpful comments. The financial support of the Swiss National Science Foundation (grant nr. 100017_150071/1) is gratefully acknowledged. †Department of Political Science, University of Zurich (http://www.fabriziogilardi.org/). ‡Department of Political Science, University of Michigan (
[email protected]). §Department of Political Science, University of Zurich (
[email protected]). 1 1 Introduction A large number of studies have examined how policies in one country, state, or city are shaped by policies in other countries, states, or cities—that is, how policies diffuse, cross-nationally or sub-nationally (Dobbin, Simmons and Garrett, 2007; Gilardi, 2012; Graham, Shipan and Volden, 2013; Maggetti and Gilardi, 2015).