down by age, gender, country of birth, sector of apprehension along the border, and time period (e.g., month and year). The panel believes that USBP would be able to release a much more complete individual-level file by implementing masking methods for problematic fields in the records and by releasing data with sufficient delay, for example a full year, to diminish their sensitivity for operational use and deployment.

It should be noted that there are other mechanisms in addition to properly constructed public use files for providing researcher access to data while protecting privacy. These mechanisms include: establishing one or more secure enclaves for researchers to access microdata, similar to the U.S. Census Bureau’s network of Research Data Centers or its National Science Foundation–Census Research Network; developing remote, monitored online data access services such as the system maintained by the National Center for Health Statistics (NCHS); and providing licenses to individual researchers for using confidential data at their institutions, as is done by the National Center for Education Statistics (NCES). However, these systems, unlike the construction of one or more public use files, require a level of staff and resources that would likely be difficult for DHS to establish and maintain over a sustained period. Given the basic nature of the information included in the DHS enforcement administrative databases and the population in question (i.e., unauthorized border crossers), DHS’s confidentiality and privacy concerns may also be different from those of NCHS, NCES, and the Census Bureau.

•   Recommendation 5.1: DHS should integrate apprehensions data from USBP, OFO, and ICE for analytical purposes.

•   Conclusion 5.1: Administrative data from DHS are alone insufficient to estimate the flow of unauthorized migrants across the U.S.–Mexico border. However, they could be combined with survey data to produce useful insights about migrant flows and the effectiveness of border enforcement. The use of modeling approaches in conjunction with disaggregated survey and administrative data is necessary for estimating these flows.

•   Recommendation 5.2: DHS should sponsor and conduct research on modeling approaches for estimating the flows of unauthorized migrants across the U.S.–Mexico border.

•   Conclusion 5.2: DHS would greatly benefit from making the administrative data from its immigration enforcement databases



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