Research

Working Papers*

Mobility and Migration Amid the Taliban Insurgency

This paper uses anonymous cell phone data to measure the change in human mobility following exposure to insurgent violence. Using call detail records (CDR) from more than 15,000 cell phone users over a 17-month period, we analyze patterns of civilian movement and migration during a period of Taliban insurgency in Afghanistan (2011-2012). These call detail records, paired with a unique violent events dataset, provide behavioral and economic context in an otherwise data-scarce conflict setting. Our results point to a small negative effect of exposure to violence on measures of mobility. We introduce a method for inferring international migration from CDR data. Preliminary results suggest an increase in the likelihood of migration with additional exposures to insurgent violence.

Internet Access and Immigration: Evidence From Mexico

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 (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 of working papers available upon request.

Selected Work In Progress

Enforcement and the Public Lives of Immigrants

Fertility Effects of a Financial Crisis (with Mayra Pineda Torres)