Friday, October 22, 2021

What’s the Relation Between Border Apprehensions and Unauthorized Entries? Part 2

In Part 1 we considered the official numbers for apprehensions at the Mexico-U.S. border and how the meaning of those numbers fluctuates over time. Now we’ll consider ways to estimate the number of unauthorized border crossers who become part of the general U.S. population—that is, the ones who either evade apprehension or are allowed to remain after apprehension.

For these numbers we need to use estimates based on various sources. As with the apprehension numbers, the metrics for the data in these sources aren’t necessarily consistent over time. Adding to our difficulties, most government data uses the U.S. fiscal year, which begins in October, while other sources may use the calendar year, or even comparisons between certain months.


We will note these discrepancies but won’t try to adjust for them. All estimates will be rounded to the nearest thousand.

 

Calculating Changes in the Undocumented Population

One way to estimate the number of successful border crossers is to study changes in the size of the undocumented population.

 

The traditional approach to determining this population’s size is the residual method. Demographers start from the estimated number of immigrants in Census Bureau’s annual American Community Survey (ACS), subtract the number of naturalized citizens and green card holders, make adjustments for underreporting, and come up with an estimate for the undocumented population in that year. (Note: the ACS is based on the calendar year.)

 

Conservatives frequently claim this method undercounts the undocumented population, but it has proved itself in a real-life test: the “amnesty” of 1986. The number of migrants applying for legalization was within the range the residual method predicted. Since then a number of refinements have led to more detailed ACS-based estimates.

 

A further refinement of the residual method is presented by demographers Robert Warren and John Robert Warren in a 2013 paper. In addition to estimating the size of the undocumented population from 1990 to 2009, they break out estimates for the number of unauthorized migrants that entered the country each year and the number that left the count—by emigrating, adjusting their status, being deported, or dying. The year of entry is provided by the ACS, and DHS supplies the number of those who adjusted status or were deported; mortality is based on standard mortality rates for Latino males based on age.

 

The Warren and Warren estimates, which run from 1990 through 2009, form a pattern not too far from that of border apprehensions. The growth rate for the undocumented population reached a high point in 2000 and then declined; by 2008 the number of people leaving the undocumented population exceeded the number that entered.

 

Source: ProCon, based on Pew Research reports

Two other studies show that the decline continued for at least the next decade: a summary of estimates through 2017 by Pew Research, and unpublished data supplied by the Center for Migration Studies (CMS) extending the Warren and Warren estimates to 2016.

 

But What About the Overstays?

However, estimates of the undocumented population don’t tell us how many of these migrants entered by crossing the southwestern border. Many undocumented migrants enter with a visa but overstay the visa’s expiration date; if they stay permanently, they become part of the undocumented population.

 

In recent years this group may have surpassed border crossers as a share of new undocumented arrivals.

 

The main source for an overstay count is an annual “entry/exit overstay” report from DHS. The report for fiscal 2016  shows 50,437,278 entries by foreigners who were issued visas for limited stays or were allowed to enter through the Visa Waiver Program. The department subtracts the number of visa holders who adjusted their status—received new visas or applied for permanent residence—and estimates the number of visa holders who exited the country before their visas expired. The result is what DHS calls 739,478 “overstay events.” Subtracting people who simply overstayed by a few months or less, DHS comes up with a 628,799 “suspected overstays.”

 

But these numbers are educated guesses, as is shown by the term “suspected overstays.” The government has a system for tracking people entering with visas, but tracking people leaving is more difficult. Most enter and leave by air, along with some who travel by sea, so it’s possible to track exits by consulting passenger manifests, but matching the tens of millions of visa holders with the tens of millions of manifests is a monumental task. And tracking is even more difficult for the visa holders who enter and leave by land—mostly Canadians and Mexicans.

 

There are other hurdles to estimating overstays. People who receive more than one visa in the course of a year can overstay more than one time in a year, thus getting counted more than once, and visa holders who die while in the US—elderly parents visiting their children, for example—might be counted as overstays.

 

Correcting the Overcount

DHS’s estimate is a significant overcount, according to demographer Robert Warren, who is Senior Visiting Fellow at CMS. Warren uses the ACS data, including a breakdown by national origin, to adjust the DHS overcount and provide a new estimate. Warren and CMS Executive Director Donald explain the method in a 2018 article, and Warren describes the results in an accompanying article. The number Warren comes up with for 2016 is 306,000, less than half the DHS number.

 

Source: Center for Migration Studies

If we take this 2016 overstay estimate in conjunction with CMS’s 623,000 estimate for that year’s unauthorized arrivals, then these 306,000 overstays would account for 49 percent of the arrivals, while 317,000 migrants had presumably entered the U.S. population by crossing the border without authorization.

 

Warren gives somewhat different figures in a 2019 CMS report, estimating arrivals at 515,000 arrivals and overstays at 320,000, or 62 percent. By this estimate, only 195,000 migrants—or 38 percent of total arrivals—had entered the U.S. population in 2016 by crossing the border without authorization.


Part 1: http://thepoliticsofimmigration.blogspot.com/2021/08/whats-relation-between-border.html

Part 3: http://thepoliticsofimmigration.blogspot.com/2021/08/whats-relation-between-border_26.html

Part 4: http://thepoliticsofimmigration.blogspot.com/2021/08/whats-relation-between-border_28.html


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