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August 16th, 2013 6:05 pm
That Pesky Denominator
Posted by Print

Here’s the thing about all that money we spend on immigration enforcement: we don’t know if any of it actually works. From Fox News:

Despite Washington spending billions of taxpayer dollars on efforts to secure the U.S.-Mexico border, two internal government reports reveal there is no clear way of gauging whether any of it is actually working.

Backing up reporting from Fox News earlier this year, the reports from the Government Accountability Office and the Congressional Research Service show the Department of Homeland Security lacks an accurate barometer to measure the success of ramped-up efforts to curtail illegal crossings.

Wasteful, inefficient government at work again? Well, not really.

“Apprehensions data are imperfect indicators of illegal flows because they exclude two important groups when it comes to unauthorized migration: aliens who successfully enter and remain in the United States … and aliens who are deterred from entering the United States,” Marc Rosenblum, immigration policy specialist at CRS, wrote in his May report. “Thus, analysts do not know if a decline in apprehensions is an indicator of successful enforcement, because fewer people are attempting to enter, or of enforcement failures, because more of them are succeeding.”

The report said recent drops in illegal immigration can likely be attributed to a combination of enforcement and the economic downturn in the U.S., “though the precise share of the decline attributable to enforcement is unknown.”

In other words, to borrow from Donald Rumsfeld, we’re dealing with a “known unknown.” That is, by definition, the only data we have is on people that we’ve stopped. The ones who get through obviously don’t get counted. So we known the numerator with no idea as to the size of the denominator.

There isn’t really a policy fix to this problem. Stepping up enforcement may reduce the number of illegals that get through, but we’ll never be able to do more than make rough estimates as to how much of the overall attempted inflow they represent.

Thus, the lesson here isn’t so much that you can’t trust government to do it’s job (though you can generally take that as a given); It’s that you should take any claims about dramatic successes in securing the border with about 10,000 grains of salt. The statistics always look good when you get to record all your successes without reference to your failures.

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