Putting TRAC to Work
  Legal and Scholarly
Harvard Law School
May 21, 2018

Beyond the Border and Into the Heartland: Spatial Patterning of U.S. Immigration Detention
By Margot Moinester

TRAC Fellow Margot Moinester's study draws on two sets of administrative records obtained through Freedom of Information Act (FOIA) requests by the Human Rights Watch and the Transactional Records Access Clearinghouse (TRAC). The first captures the detention history of each individual detained by ICE or its predecessor (the INS) between October 1, 1998 and May 25, 2010. The files contain records for each booking of a detainee into or out of a facility. Fields include the first-ever detention date, apprehension date, apprehension location, facility name and location, entry and exit dates from the facility, a code for the reason for exit, and the detainee’s gender and citizenship country. Each record thus refers to a single detention event, such as a deportation or transfer, and together such records make up individual detention episodes. Although the data do not include an individual identifier, she use the order of records and consistencies between several variables to identify unique detention episodes. The second data set is similarly structured but, in lieu of apprehension location, includes information about the charge leading to detention, whether the detention is mandated under the mandatory detention statute, whether a final order of removal is issued, the detainees' legal status at the time of entry into the United States,and the date the detainee first entered the United States. The second data set covers all detentions between October 1, 2006 and December 31, 2011. Combined, the two data sets include 3,308,091 detention episodes, with an average of two detention booking events per episode. She restricts the analysis to the 717,160 detention episodes beginning in 2008 and 2009 because these years capture interior enforcement at its peak, when more than 60% of removals originated in the interior before dropping to approximately 30% in 2015 (DHS2015). These years also contain the most complete information on apprehension locations. The appendix details the merging process across the two data sets and other coding procedures through which precise matches were found for 643,425 episodes, 89.72% of all detentions. Of these matched records, 90.0% contain complete data on all variables used in the regression analysis.

Transactional Records Access Clearinghouse, Syracuse University
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