EMIF-N—would still raise concerns regarding Mexican-side implementation and low and erroneous response rates, similar to those that would be raised if DHS were to be involved in a Mexican-side household survey.7
• Recommendation 4.1: For the purpose of estimating unauthorized migration flows across the U.S.–Mexico border on an annual or quarterly basis, DHS should not invest substantial resources in making major changes to existing surveys or in implementing a new survey.
• Conclusion 4.1: Existing surveys are subject to a variety of limitations having to do with target populations and associated issues of sample size and survey design, the frequency with which surveys are conducted and the speed with which data are made publicly available, and the types of questions that are asked about migration. Therefore, although survey data are critical for understanding patterns and general trends in unauthorized migration, they will not be sufficient by themselves to meet the needs of DHS for estimating unauthorized migration flows across the U.S.–Mexico border.
• Conclusion 4.2: Implementing a new household survey that meets the needs of DHS would require an investment at least comparable to that associated with the American Community Survey in the United States; any such survey would also have to fall within the purview of the Government of Mexico. A survey that uses a time-location design and focuses directly on migrant populations (e.g., EMIF-N) would be more promising, but such a non-traditional design would necessitate careful adherence to the sampling protocol and, in particular, would require that concerns about coverage error be addressed. Mexican-side implementation would also be an issue. Substantial modifications of existing general household or specialty migration surveys to meet the needs of DHS would encounter similar challenges. These challenges are only magnified by the complex and dynamic nature of the underlying migration process.
The next chapter explores the usefulness and limitations of another approach: the use of DHS administrative data as they relate to the estimation of unauthorized migration flows across the U.S.–Mexico border.
7 Sample sizes and financial costs would also be significantly smaller for an EMIF-N-like design than they would for a nationwide Mexican household survey.