Tag Archives: population

The U.S. government asked 2 million Americans one simple question, and their answers will shock you

What is your age?

[SKIP TO THE END for a mystery-partly-solved addendum]

Normally when we teach demography we use population pyramids, which show how much of a population is found at each age. They’re great tools for visualizing population distributions and discussing projections of growth and decline. For example, consider this contrast between Niger and Japan, about as different as we get on earth these days (from this cool site):

japan-niger-pyramids

It’s pretty easy to see the potential for population growth versus decline in these patterns. Finding good pyramids these days is easy, but it’s still good to make some yourself to get a feel for how they work.

So, thinking I might make a video lesson to follow up my blockbuster total fertility rate performance, I gathered some data from the U.S., using the 2013 American Community Survey (ACS) from IPUMS.org. I started with 10-year bins and the total population (not broken out by sex), which looks like this:

totalbinned

There’s the late Baby Boom, still bulging out at ages 50-59 (born 1954-1963), and their kids, ages 20-29. So far so good. But why not use single years of age and show something more precise? Here’s the same data, but showing single years of age:

totalsingleyears

That’s more fine-grained. Not as much as if you had data by months or days of birth, but still. Except, wait: is that just sample noise causing that ragged edge between 20 and about 70? The ACS sample is a few million people, with tens of thousands of people at each age (up age 75, at least), so you wouldn’t expect too much of that. No, it’s definitely age heaping, the tendency of people to skew their age reporting according to some collective cognitive scheme. The most common form is piling up on the ages ending with 0 and 5, but it could be anything. For example, some people might want to be 18, a socially significant milestone in this country. Here’s the same data, with suspect ages highlighted — 0’s and 5’s from 20 to 80, and 18:

totalsingleyearsflagged

You might think age heaping results from some old people not remembering how old they are. In the old days rounding off was more common at older ages. In 1900, for example, the most implausible number of people was found at age 60 — 1.6-times as many as you’d get by averaging the number of people at ages 59 and 61. Is that still the case? Here it is again, but with the red/green highlights just showing the difference between the number of people reported and the number you’d get by averaging the numbers just above and below:

totalsingleyearsflaggedhighlightProportionately, the 70-year-olds are most suspicious, at 10.8% more than you’d expect. But 40 is next, at 9.2%. And that green line shows extra 18-year-olds at 8.6% more than expected.

Unfortunately, it’s pretty hard to correct. Interestingly, the American Community Survey apparently asks for both an age and a birth date:

acs-age

If you’re the kind of person who rounds off to 70, or promotes yourself to 18, it might not be worth the trouble to actually enter a fake birth date. I’m sure the Census Bureau does something with that, like correct obvious errors, but I don’t think they attempt to correct age-heaping in the ACS (the birth dates aren’t on the public use files). Anyway, we can see a little of the social process by looking at different groups of people.

Up till now I’ve been using the full public use data, with population weights, and including those people who left age blank or entered something implausible enough that the Census Bureau gave them an age (an “allocated” value, in survey parlance). For this I just used the unweighted counts of people whose answers were accepted “as written” (or typed, or spoken over the phone, depending on how it was administered to them). Here are the patterns for people who didn’t finish high school versus those with a bachelor’s degree or higher, highlighting the 5’s and 0’s (click to enlarge):

heapingbyeduc

Clearly, the age heaping is more common among those with less education. Whether it’s really people forgetting their age, rounding up or down for aspirational reasons, or having trouble with the survey administration, I don’t know.

Is this bad? As much as we all hate inaccuracy, this isn’t so bad. Fortunately, demographers have methods for assessing the damage caused by humans and their survey-taking foibles. In this case we can use Whipple’s index. This measure (defined in this handy United Nations slideshow) takes the number of people whose alleged ages end in 0 or 5 and multiplies that by 5, then compares it to the total population. Normally people use ages 23 to 62 (inclusive), for an even 40 years. The amount by which people reporting ages 25, 30, 35, 40, 45, 50, 55, and 60 are more than one-fifth of the population ages 23-62, that’s your Whipple’s index. A score of 100 is perfect, and a score of 500 means everyone’s heaped. The U.N. considers scores under 105 to be “very accurate data.” The 2013 ACS, using the public use file and the weights, gives me a score of 104.3. (Those unweighted distributions by education yield scores of 104.0 for high school dropouts and 101.7 for college graduates.) In contrast, the Decennial Census in 2010 had a score of just 101.5 by my calculation (using table QT-P2 from Summary File 1). With the size of the ACS, this difference shouldn’t have to do with sampling variation. Rather, it’s something about the administration of the survey.

Why don’t they just tell us how old they really are? There must be a reason.

Two asides:

  • The age 18 pattern is interesting — I don’t find any research on desirable young-adult ages skewing sample surveys.
  • This is all very different from birth timing issues, such as the Chinese affinity for births in dragon years (every twelfth year: 1976, 1988…). I don’t see anything in the U.S. pattern that fits fluctuations in birth rates.

Mystery-partly-solved addendum

I focused one education above, but another explanation was staring me in the face. I said “it’s something about the administration of the survey,” but didn’t think to check for the form of survey people took. The public use files for ACS include an indicator of whether the household respondent took the survey through the mail (28%), on the web (39%), through a bureaucrat at the institution where they live (group quarters; 5%), or in an interview with a Census worker (28%). This last method, which is either a computer-assisted telephone interview (CATI) or computer-assisted personal interview (CAPI), is used when people don’t respond to the mailed survey.

It turns out that the entire Whipple problem in the 2013 ACS is due to the CATI/CAPI interviews. The age distributions for all of the other three methods have Whipple index scores below 100, while the CATI/CAPI folks clock in at a whopping 108.3. Here is that distribution, again using unweighted cases:

caticapiacs

There they are, your Whipple participants. Who are they, and why does this happen? Here is the Bureau’s description of the survey data collection:

The data collection operation for housing units (HUs) consists of four modes: Internet, mail, telephone, and personal visit. For most HUs, the first phase includes a mailed request to respond via Internet, followed later by an option to complete a paper questionnaire and return it by mail. If no response is received by mail or Internet, the Census Bureau follows up with computer assisted telephone interviewing (CATI) when a telephone number is available. If the Census Bureau is unable to reach an occupant using CATI, or if the household refuses to participate, the address may be selected for computer-assisted personal interviewing (CAPI).

So the CATI/CAPI people are those who were either difficult to reach or were uncooperative when contacted. This group, incidentally, has low average education, as 63% have high school education or less (compared with 55% of the total) — which may explain the association with education. Maybe they have less accurate recall, or maybe they are less cooperative, which makes sense if they didn’t want to do the survey in the first place (which they are legally mandated — i.e., coerced — to do). So when their date of birth and age conflict, and the Census worker tries to elicit a correction, maybe all hell breaks lose in the interview and they can’t work it out. Or maybe the CATI/CAPI households have more people who don’t know each other’s exact ages (one person answers for the household). I don’t know. But this narrows it down considerably.

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Jonathan Last could live with barefoot-and-pregnant

I was replaced on the guest list for KCRW’s To the Point discussion about Jonathan Last’s book, What To Expect When No One’s Expecting: America’s Coming Demographic Disaster. But before I was cut I did some preparation — read some of the book and made some notes.

Last is a writer for the Weekly Standard (in which capacity he recently suggested that, rather than try to reach out to single people, the GOP should instead work on convincing more people to get married), who also wrote for First Things, a Christian conservative website. His essay in the Wall Street Journal sparked my initial post, but the book is more extreme than that column was.

Last doesn’t add substantively to the general concern that below-replacement fertility causes problems, except to exaggerate it cartoonishly for the U.S. (“The root cause of most of our problems is our declining fertility rate”). The historical perspective is so weak here I feel the need to remind him that caring for aging Baby Boomers is a problem not of low fertility but high fertility. Were it not for the high fertility of the Baby Boomers’ parents, we would have had gradually declining long-run fertility levels and a working-age population much more up for the task of funding Medicare and Social Security.

In the book he relies heavily on Phillip Longman, the author of “The Empty Cradle,” whom I’ve written about before, but also summons (without mentioning it) Charles Murray’s Coming Apart, which bemoans the divergent family structures of middle- and working-class White America and chastises the rich for being too self-absorbed and pleasure-driven to keep up their responsibilities as moral compasses. Thus, he tuts:

The bearing and raising of children has largely become the province of the lower classes.

Last and Longman are helping the American patriarchal right get its desire for “traditional” family structures in sync with corporate America’s amoral economic growth obsession, and it turns out boosting fertility is a message they can all get behind (plus it pleases both evangelical Protestant and conservative Catholic culture warriors).

last-cover-adapt

My adaptation of the book cover art.

Gender

Of course, fertility rates in the U.S. fell after the Baby Boom as women’s employment rates and educational  attainment increased. And those women with better opportunities have fewer children, on average. (However, this relationship is not universal or inevitable — see developments in Norway, for example.) But Last doesn’t want to create the impression that his wish for higher fertility implies opposition to women’s progress.

I’d also like to offer a preemptive defense against readers who may take this book to be a criticism of the modern American woman. Nothing could be further from my intent. … The more educated a woman is, on average, the fewer children she will have. To observe this is not to argue that women should be barefoot, pregnant, and waiting at home for their husbands every night with a cocktail and a smile.

But that he suggests we have more children — without taking steps to reconcile our endemic work-family conflicts and persistent gender imbalances (he’s not advocating universal childcare or healthcare, better welfare, paid family leave or a shorter workweek) — means that even if he’s not arguing for a return to barefoot-and-pregnant status, he’s at least willing to live with it.

Innovation

His passing nod to Esther Boserup was interesting to me. Writing in the 1960s and 1970s (which Last carelessly calls “a century ago,” after apparently skimming her Wikipedia entry), Boserup argued that population pressure spurred agricultural innovation. That is, farmers figured out how to rotate land more efficiently, for example, when there was more demand for farmland (and food). I don’t know how well this theory is holding up in the historical scholarship (I don’t think it explains European divergence from China, for example) but it is interesting — and we’ve now spent as much time thinking about it as Last did).

From this Last declares that the reverse is also true, that postindustrial societies suffer a lack of innovation when populations shrink. That is a question Boserup was unlikely to have troubled herself with (but let me know if I’m missing something she wrote on it). However, I could conjure the opposite hypothesis – that a rapidly shrinking population would spur a different kind of innovation in postindustrial society. For example, we may face pressure for old people to be more productive, as they delay retirement; and to invest more wisely (and heavily) in the smaller cohorts of children’s education and skill development.

Immigration

Last goes out of his way to say (perhaps too much) that he’s not against immigration, without which American fertility rates would be much lower.  He is just against the immigration of people who don’t assimilate into America’s Christian majority. He writes:

A reasonably liberal program of immigration is necessary for the longterm health of our country. Yet at the same time, this liberal approach to immigration should be coupled with a staunchly traditionalist view of integration. America has been lucky in the way it has assimilated most of its immigrants. Europe—and France in particular—has not. “Europe” as we have known it for 15 centuries is almost certain to fade away in the next 50 years, replaced by a semi-hostile Islamic ummah. All that will remain of what we traditionally know as “Europe” is the name [It’s not clear why the hostile Islamic majority of 2063 would retain the name “Europe” -pnc]. This change was not inevitable; it is the result of a policy choice made by adherents of a truly radical faith: multiculturalism. … Tolerance need not be surrender and a certain amount of cultural chauvinism is necessary for societal coherence.” (p. 169)

“Racism” is the wrong term for this attitude. I guess his term “cultural chauvinism” is accurate because it assumes a cultural superiority. But that doesn’t quite capture the animus. Anyway: If the problem is falling fertility, why worry about the culture that the fertile immigrants bring? It’s just possible that Last’s problem is not just with fertility.

Religion

Like Longman, Last is sad about the demise of religion in the “public square,” which reduces fertility. In this he reveals his apocalyptic Christian moorings:

Of all of the evolutions in twentieth-century America, the most consequential might be the exodus of religion from the public square.

Really. More consequential than civil rights, women’s rights, science, public health, militarism and Wall Street? And isn’t exodus a strong word for what’s happened? There’s only one reason to believe a moderate decline in religiosity is more important than anything else: Because God said so. Anyway, besides ending the War on Christmas, Last also wants us to give credit for births where it is due (to God).

America is the most demographically healthy industrialized nation; it is also the most religiously devout. This is not a coincidence. … There is no reason for wishing the United States to be a theocracy. That said, it is important we preserve the role of religion in our public square, resisting those critics who see theocracy lurking behind every corner. Our government should be welcoming of, not hostile to, believers—if for no other reason than they’re the ones who create most of the future taxpayers. After all, there are many perfectly good reasons to have a baby. (Curiosity, vanity, and naïveté all come to mind.) But at the end of the day, there’s only one good reason to go through the trouble a second time: Because you believe, in some sense, that God wants you to.

I guess that means atheists don’t have a good reason to have more than one child. (Are there multiple-child atheists out there to respond to this?) Anyway, it’s usually not a good sign when an author follows “There is no reason for wishing the United States to be a theocracy,” with, “That said…”

Transportation

We can see the depth of Last’s commitment to the long term in his discussion of transportation. One reason New Englanders and other liberals don’t have enough children, he believes, is because land is too expensive where they live. So they have small houses and long commutes, which aren’t conducive to child-rearing.

The answer is not more public transportation. Light rail might work for the child-free. (Or it might not; there is a stark divide in the literature on mass transit.) But parents trying to balance work and children need the flexibility automobiles provide; they cannot easily drop a child at a babysitter or school, then take a train to work, then train home, and then fetch the child. (If you don’t believe me, you try it.) The solution is building more roads.

That’s our destiny? A more efficient suburban sprawl to nurture our larger families? Doesn’t he care about climate change? Maybe, maybe not. He writes in a footnote:

The only environmentalist concern that population [growth] might legitimately affect is climate change, a subject so fraught with theological division that I’ll leave it be.

What courage, refusing to genuflect the climate-change authorities like that. And yet what cowardice to refuse to take a position in the face of “theological division.” That’s some combination.

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Read it and weep : Demography I syllabus

Never one to wait till the last minute, I completed the syllabus for my graduate seminar with more than 12 hours to spare.

At UNC the sociology department offers a two-seminar series for students starting out with a concentration in demography, which is also standard for predoctoral trainees at the Carolina Population Center. The course has passed around the department, offering the best of our different perspectives — as well as the risk of inertia. I overhauled it quite a bit, but it still owes lots to Lisa Pearce and Anthony Perez, who taught it most recently.

Took me a long time. But what a moment! Looking down the list of two books and 55 other required or optional readings over 13 weeks, I think: how much would you know if you really read all that? And also: there’s probably no one in the world (not even me) who’s read this combination of things before. Etc.

Here’s a teaser: one graph I made for illustrating population growth. It replicates one John Bongaarts made in 1975, showing where the countries of the world lie on the birth-rate / death-rate axis. Bottom line: when birth rates are higher, population grows. The other 54+ readings are details…

I was happy to add a new book this year: Mara Hvistendahl’s Unnatural Selection: Choosing Boys over Girls, and the Consequences of a World Full of Men. I still plan to post a review here, but let me just say it’s a great example of accessible science writing about demography. It’s well-documented and thorough but also compelling to read and does a great job motivating the issue. (Sure, she overreaches, too. That’s OK.)

Here’s the syllabus; some of the links to the readings will run into pay walls if you’re off campus. I will be updating it with the assignments over the semester — fell free to play along at home…

I hope everyone who has one, has a good fall semester.

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