of the target population. Statistical inferences are affected by nonsampling errors, such as coverage, measurement, and non-response errors. Survey researchers often use weighting procedures to account for the features of the sampling design and make adjustments for non-response or coverage error.

For the purposes of this report, it is important to determine how well the existing surveys are designed, in order to assess their usefulness. The surveys described are conducted in the United States, in Mexico, or both, and the panel evaluated them to determine their effectiveness in estimating both the number of foreign nationals who attempt illegal entry across the U.S.–Mexico land border and the probability of apprehension of illegal entrants. Our evaluation also addresses the possibility of obtaining these estimates on a quarterly basis for particular regions of the U.S.–Mexico border.

This chapter outlines the features of the major surveys in the United States and Mexico (summarized in Table 3-1) that collect information about migration and border crossing; details about some of the specific questions asked by the surveys are provided in Appendix A. Chapter 4 discusses the usefulness and limitations of these surveys in estimating the number of foreign nationals who attempt illegal entry across the U.S.–Mexico land border.


The American Community Survey (ACS) conducted by the U.S. Census Bureau is intended to collect data comparable with the Census 2000 long-form sample data, but to do so every year rather than every 10 years (Grieco and Rytina, 2011). Information from the ACS is used to administer federal and state programs and distribute federal funds. The survey asks about age, gender, race, family and relationships, income and benefits, health insurance, education, veteran status, disabilities, where people work and how they get there, where people live, and how much people pay for certain essentials. Fully implemented since 2005, the ACS collects annual data in twelve monthly samples. The target population of the ACS is the entire resident population of the United States and Puerto Rico. The sampling frame reflects this target population by identifying all addresses of households for the 2005 ACS and all addresses of both households and group quarters for the ACS since 2006. Data collection uses three modes that take place over a 3-month period: mail, telephone, and personal visit. The target population for the ACS only includes people who are deemed to be residents of the United States; short-term migrants, such as many undocumented Mexican workers, would not be part of the ACS universe.

The 2010 Public-Use Sample, which is a 1 percent sample of the U.S. population, included 1,204,000 households and 3,062,000 respondents. Of these, 145,000 households were immigrant households (35,000 Mexican

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