A New Model for Path Data: Analyzing Sectarianism & Segregation on the Streets of Baghdad
Dean Knox, MIT, Political Science
Path data describes the steps that an actor takes to get from point A to B. It offers researchers the opportunity to test theories about network navigation, e.g. in social and geographic networks. For example, path data can show whether individuals avoid out-group neighborhoods in their daily walking routes, resulting in societal inefficiencies and reducing inter-group contact. This data can also reveal how voters search social networks for political information, which may distort the information they ultimately receive. However, the sequential decision-making process in path data violates the underlying assumptions of existing models, which assume some form of conditional independence between observations. I propose a new random-path model (RPM) that explicitly captures this pathwise dependence, develop an estimation procedure, and demonstrate its properties. The RPM builds on a random-walk model, incorporating a realistic but difficult-to-analyze constraint to account for the fact that actors are purposefully navigating toward a destination. I validate the model in an analysis of the U.S. Interstate Highway planning process, where existing approaches fail to recover a known qualitative benchmark. Finally, the RPM is used to test two competing explanations of Baghdad's recent segregation. Using smartphone-based behavioral data from Sunni and Shia participants in a field activity, I show that a need-based model of residential sorting---when families flee mixed neighborhoods to avoid political violence---is insufficient to explain participants' walking routes alone. Instead, their choices reveal that conflict has also created significant taste-based aversion to out-groups in a city once known for its cosmopolitanism. These results suggest that societal preferences have shifted in a way that makes Baghdad's eventual re-integration unlikely.
November, 14 2016 | 12:45 p.m. - 2:00 p.m. | Gross Hall 230E