More Details on the 2016 Population Estimates
Census Changed Their Emigration Estimates
This post is a follow-up to my earlier post about Census 2016 population estimates on two key points: the issue of revisions, and a deeper-dive on international migration, two areas where I got questions.
Why Did International Migration Change So Much?
Regular readers will recall that I have had some skepticism over Census’ estimates of emigration, that is, international outflows. I have argued in the past that they underestimate emigration. My main argument has been that Census undercounts the emigration of US-born people, because I had solid data on that question. I have also long believed Census probably understates foreign-born emigration.
Census seems to have come around to this view as well!
So there it is. Census had previously been carrying group-level emigration estimates that were negative, and swapping in zeroes. This helps explain the anomaly that many people have noticed, namely, that for county-level estimates, very few US counties have negative net international migration. It seems plausible that when county estimates are released, we will see more counties in the red, suggesting we may see wider variability in county-level net international migration estimates.
For your viewing pleasure, here’s a map of where net international migration estimates changed, and by how much:
As you can see, areas with dense Mexican and Asian populations got hit the hardest, as you would expect from the notes that Census provided.
Given the note and the size of the change, this revision really should be the story from this round of estimates. This scale of revision is, in my view, larger than typical, and likely to have more downstream effects throughout the estimates than is typical.
Why Care So Much About Revisions?
I have discussed this topic at length in the past. I don’t feel like repeating myself that much, so go read that post from the 2015 estimates.
But the simple version is this: most-recent-year estimates are just that — estimates! They change! They are Census’ best guess, and they do a fairly good job, but finding instances where Census’ first estimate was wildly off base is childsplay. It’s not just that; for local areas, the last, most updated Census vision is not-infrequently wildly off from Census figures! This isn’t because they are doing something wrong, but because they have a hard job and are expected to produce estimates on a very short timeframe. I mean geez I certainly can’t come up with a vastly more compelling estimate for Delaware’s population in July of 2016 than theirs!
And since they have to make these estimates for every state, region, city, county, incorporated place, metropolitan area… even if they hit the target 95% of the time there will still be thousands of cases where they were off-base, especially on their first round of estimates.
As long as I’m writing, I will be beating on the “revisions matter more than new-year estimates” drum.
The new-year estimates are good enough and fill a valuable role. But they reflect a low degree of certainty. Back-year estimates, especially for large areas like states, reflect a much higher degree of certainty, and thus should be taken more seriously and given more thoroughgoing attention and analysis.
Check out my Podcast about the history of American migration.
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I’m a native of Wilmore, Kentucky, a graduate of Transylvania University, and also the George Washington University’s Elliott School. My real job is as an economist at USDA’s Foreign Agricultural Service, where I analyze and forecast cotton market conditions. I’m married to a kickass Kentucky woman named Ruth.
My posts are not endorsed by and do not in any way represent the opinions of the United States government or any branch, department, agency, or division of it. My writing represents exclusively my own opinions. I did not receive any financial support or remuneration from any party for this research.
