To Make Policy You Need Facts

Two Yale profs, Edward Kaplan and Jonathan Feinstein, have published a study that suggests that the number of immigrants in the United States illegally may be double the official estimates. From Yale Insights:

Using mathematical modeling on a range of demographic and immigration operations data, the researchers estimate there are 22.1 million undocumented immigrants in the United States. Even using parameters intentionally aimed at producing an extremely conservative estimate, they found a population of 16.7 million undocumented immigrants.

The results, published in PLOS ONE, surprised the authors themselves. They started with the extremely conservative model and expected the results to be well below 11.3 million.

“Our original idea was just to do a sanity check on the existing number,” says Edward Kaplan, the William N. and Marie A. Beach Professor of Operations Research at the Yale School of Management. “Instead of a number which was smaller, we got a number that was 50% higher. That caused us to scratch our heads.”

The eye-catching graphic from the article is reproduced above. What it illustrates is that the number of people here illegally is something between 16 million and 35 million and the official estimate of 11 million is not only wrong but very wrong.

The authors of the study’s conclusion is exactly the right one: to make policy you need to know the scale of whatever you’re dealing with.

This study doesn’t just have implications for immigration policy. It affects policy across a wide range of issues—immigration, health care, housing, transportation, and infrastructure. Our policies need to be designed for the world as it is not the world of our hopes or our fears.

We should start measuring a variety of indirect sources—highway and public transport utilization, water and sewer use, and the like. Clearly, we need better estimates.

10 comments… add one
  • steve Link

    Always leery of drawing conclusions based upon one study. They may be correct, but would like to see confirmation study. That said, couldn’t agree more that it is hard to make good policy w/o the facts.

    I sometimes wonder if the rest of the world is as bad as what I often see in medicine. People come to me wanting more of something (people, services, time, whatever), but they almost never come with metrics showing that they actually need more of what they want.


  • They may be correct, but would like to see confirmation study.

    Me too.

  • Ben Wolf Link

    Maybe some good news from the model:

    He points out that previous studies, based on the widely accepted total of 11.3 million undocumented immigrants, found that the rate of serious crimes committed by these immigrants is lower than for U.S. citizens. The new findings suggest that the rate is even lower than previously believed: “You have the same number of crimes but now spread over twice as many people as was believed before, which right away means that the crime rate among undocumented immigrants is essentially half whatever was previously believed.”

  • Possible but indeterminate. The clearance rate for all crimes has plummeted over the last 30 years. That means that we have no idea who perpetrated them.

  • Gray Shambler Link

    My personal experience says we have about 40 million undocumented people in the U. S. How did I come by this number? I’m a Driver. as I pass through town, I estimate that 15% of the workers and people I see appear to be Mestizo. In Lincoln, (320,000), that equals 48,000. Nationwide, @ 330,000,000, it equals 49,500,000. Dropping my estimates to the low side, I still think I’m close. Good, Bad?

  • steve Link

    “still think I’m close. Good, Bad?”

    Assumes they are all illegals. That does not seem likely.


  • TastyBits Link

    If more illegal aliens are sneaking across the border, how does the total number not increase? Unless there is an equal or greater number of people leaving, the answer is, “It cannot.”

  • That does not seem likely.

    The number of work visas for which Mexicans are eligible is absurdly small—around 10,000. That’s why I keep harping on increasing the number of work visas for Mexicans.

    Mexicans apply for relatively few tourist or student visas in the U. S. No, most of the mestizos (as Gray referred to them) in the U. S. are Mexicans and most are illegal, the children of illegals, those who were legalized in the 80s, or their children.

  • steve Link

    “the children of illegals, those who were legalized in the 80s, or their children.”

    These would all be here legally. The report says illegals. If you just want to change it from illegals to people of Mexican descent, then it could be true.


  • Gray Shambler Link

    They’re not exactly sneaking either. They’re coming on foot across the desert often in large groups and if the border patrol were not there to rescue them most would die. For their efforts the Border Patrol is shamed as child abusers because they don’t just take any adult’s word about who the children belong to.

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