Research

Working Papers*


International Migration Amid Insurgent Violence (Job Market Paper)

A major challenge of empirical migration research is the simple fact that most micro-level data are constrained by international borders. While the proliferation of passively collected `digital trace' data has led to novel and useful measures of within-country migration, questions of cross-border movement remain difficult to study in many contexts. This paper develops a general method to infer international migration events from a type of anonymous cell phone metadata commonly available to researchers. I propose a set of classifying criteria from the spatial and temporal elements of call detail records to categorize attrition episodes that are plausibly due to users leaving the country through known land border crossing points. I then apply the classification method to data from a major mobile network operator in Afghanistan, linked to military records of violent events during an active period of the Taliban insurgency. Upon identifying potential migration episodes, I estimate a displacement choice model that reveals an increasing likelihood of international migration with additional exposures to violence, as expected. In addition, I show the likelihood of internal migration is unaffected by increased exposure, providing new insight into the complex role of violence as a determinant across migration types.


The Impact of Mobile Internet on Immigration: Evidence from Mexico's 3G Rollout

This paper describes the effects of the expansion of internet infrastructure on immigration between Mexico and the United States. Specifically, it asks: does the arrival of mobile internet (3G) in a Mexican municipio fundamentally change individuals' migration choice? There are several margins on which one might expect an effect--the binary migration choice itself, as well as several related decisions like optimal routes and crossing points, US destination choice, and uptake of travel aid. The project seeks to measure the relative strength of two different mechanisms within this migration choice decision. On one hand, 3G access introduces (or strengthens) an important information channel for shaping expectations of life in the destination country, and potentially avoiding risks en route. On the other hand, 3G is a valuable amenity whose addition to the home community could increase the utility of staying. Additionally, the paper examines a relevant side effect of the aforementioned information channel, namely the possibility of price convergence for the illicit services of border-crossing guides, or coyotes.


Cell Phone Coverage and Violence: Evidence from a Radio Propagation Model in Afghanistan (with Robert Gonzalez and Lin Yang)

This paper examines the impact of access to mobile phone coverage on insurgent violence. Access to coverage can lower violence by facilitating information sharing by civilians and shielding informers from retaliation. On the other hand, coverage can increase violence by reducing the cost of producing violence (e.g., facilitating coordination among insurgents, remote detonation of IEDs). Empirically, this paper finds evidence that the net effect of access to mobile phone coverage is to lower insurgent violence. We estimate a radio-wave propagation model that uses variations in terrain topography and the spatial distribution of mobile phone towers to predict signal strength on the ground for each cell of a 1X1 kilometer grid of Afghanistan. We then employ a regression discontinuity design that compares cells at the margin of the signal strength threshold required for coverage. Cells with just enough coverage experience a two percentage point drop in the likelihood of any attack and a 0.8 percentage point drop in the likelihood of an IED. Further analysis suggests that information sharing is a key mechanism. The impact of coverage is larger in cells where detection of insurgent activities by civilians is more likely: near populated areas, primary roads, and during morning hours. 


*Drafts and/or slides available upon request.

Selected Work In Progress

Enforcement and the Public Lives of Immigrants

Can Civilians Predict Insurgent Violence?

The Evolution of Hispanic Fertility Trends in the U.S. (with Mayra Pineda Torres)