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Collecting Border Statistics: Are We Getting Any Better at Measuring Border Enforcement?

Thursday, March 1, 2018

Over the last few years, the process of collecting data about illegal immigration and enforcement activities along the U.S.-Mexico border has received more attention, especially as the Trump administration has promoted data that purportedly shows a drop in the number of apprehensions along this border. In February 2015, the Bipartisan Policy Center released a report that analyzed the methods used by U.S. Customs and Border Protection (CBP) to gather border statistics and made recommendations for improving these processes, especially for data on illegal border crossers, deterrence rates, and other related immigration statistics.

In September 2017, the Office of Immigration Statistics (OIS) at the Department of Homeland Security released Efforts by DHS to Estimate Southwest Border Security between Ports of Entry, which detailed the methodology and technology currently used by CBP to record or estimate these statistics. While BPC did not contribute to the development of the report, a review of the report finds that while it appears that CBP is using methodologies similar to those recommended in the BPC report, and is taking efforts to improve its data gathering processes, the report does not include estimates of illegal entry at ports, a specific and critical recommendation in the BPC report. Nor does the DHS report address the overall estimates of the unauthorized population in the United States.

Our review found that both reports discuss methodologies for improving border statistics gathering, including adopting more technology along the border and additional metrics to collect unknown information such as changes in smuggling rates. Specifically, both reports call for using more technology along the southern border to improve known flow data, especially for “got-aways,” a metric of the number of immigrants who were identified by CBP as crossing the border but were not apprehended.

Figure 1: Overlap between BPC and OIS Data Points for Apprehensions and Illegal Entries

BPC Recommendations

OIS Report

Use similar collection methods implemented along the U.S.-Mexico border for the U.S.-Canada border

Not addressed; the report focused only on the Southwest U.S. border

Develop a new more accurate method to account for the undercount in the stock of unauthorized immigrants in the United States

Not addressed; the report did not address the estimates of the unauthorized population in the United States

Adopt more technology along the southern border to make known flow data more accurate, especially for “got-aways”

CBP is currently implementing more technology along the U.S.-Mexico border, including geospatial intelligence with the goal of increasing the accuracy of these measurements

Have information from individual DHS apprehension records available for academic and research-based purposes

Not addressed.; DHS has not yet made this data public

Have a comprehensive set of measures to analyze the number of illegal immigrants entering the United States through the ports of entry

The OIS report only reports on information/statistics related to immigration between the ports of entry

More improved estimates for the number of overstays

The OIS Report only reports data measures and procedures relevant to before and at the border activity rather than data related to internal enforcement information gathering

Focus research more to close the gap in the estimates of inflows and stock of illegal immigrants

Not addressed


However, the OIS report only provides information on apprehensions and illegal entries for areas located between ports of entry, which overlooks the effects of illegal immigration on the ports themselves. Given that these points are critical to the flow of individuals and goods along the U.S. border, future reports should specifically incorporate these metrics.

Finally, the OIS report also mentions two methods that did not appear in the BPC report: the Interdiction Effectiveness Rate and the Total Interdiction Rate. These two metrics focus on using the apprehension rate to determine how many people got stopped at the border or crossed through it. These two rates could help CBP assess the effectiveness of its enforcement measures since they track CBP’s “actual enforcement practices” such as turning back potential illegal immigrants at the U.S.-Mexico border and apprehending them if they attempt to enter the United States illegally.

In the area of improving the data gathering process, OIS specifically recommends the adoption of migrant surveys, which are primarily used to gain information about the increase in smuggling rates over the previous few decades. BPC’s report highlighted these surveys as the best option to increase reliability of estimates of those who succeed in illegal entry, but who are not observed by CBP. Both reports also called for measuring deterrence rates along the border, which measures the probability of apprehension that deters illegal immigrants from entering the United States. BPC’s report contained an extensive appendix describing the challenges and necessity of looking at overall deterrence rates. The OIS report does not measure the cost-effective levels of deterrence, which analyzes the most efficient method to promote the high levels of deterrence. Finally, the government report does not include any discussion about gathering data for the U.S.-Canada border.

Figure 2: BPC and OIS Reports on Data Gathering Processes

BPC Recommendations

OIS Report Data Points

More research will need to be conducted to determine the most cost-effective levels of deterrence at the border

Uncertain; currently DHS measures the deterrence rate with recidivism figures and migrant surveys. The report does not mention optimal cost-effective level of deterrence methods

Improve information gathering for before-the-border deterrence factors

Uncertain; information only exists for U.S.-Mexico border deportees, not for other groups

Additional analysis regarding factors that influence the decision to come to the United States that are outside the control of CBP

Yes; CBP has been collecting data regarding smugglers fees from migrant surveys


As this review shows, there are two overlaps regarding the recommendations made in the BPC report and the actual methodologies being used in the field by CBP. First, the report promotes additional analysis factors such as migrant surveys to gather new information about these flows. The report also calls for adopting more technology along the southern border to more accurately count statistics, which BPC has publicly supported. The reports’ overlaps are a welcome foundation for building and developing more concrete border statistic gathering measures.

In order to best represent the state of enforcement at the border, OIS should continue to expand its data collection efforts to other areas recommended by BPC. For instance, DHS should gather port of entry data since illegal immigrants and contraband enter through these channels as well as between the ports of entry. Further, DHS should also collect data from the U.S.-Canada border for comparison and to determine whether efforts at that border are effective. While the OIS report is a positive step in understanding activity along the U.S. border, building on our recommendations would help DHS improve its border enforcement measures by giving the agency actionable data about cross-border activity.

KEYWORDS: OFFICE OF IMMIGRATION STATISTICS, PRESIDENT DONALD TRUMP, U.S. CUSTOMS AND BORDER PROTECTION