It’s ridiculous how many expectations and conventions exist around childbirth and parenting. But over the course of writing two books about this time of life, I’ve come to appreciate that there are some things you simply can not anticipate: things people don’t talk about, sometimes because they are sad, sometimes uncomfortable, sometimes just plain weird. I think we should talk about them—and, more than that, we should use data to really understand them. (I’m an economist; I love data). Acknowledging the data can often relieve a lot of the pressure on parents, either by reflecting experiences that feel isolating in the moment or by presenting us with a greater range of choices than we might have thought we had. In that spirit, I have a series of pieces in Slate this week about how data helps illuminate childbirth and parenting’s most underdiscussed topics.
My friend Jane’s son was born three months after my own daughter. Now that they are in second grade, you’d hardly notice this age difference at all, but early on, it was hard to believe that would ever be true. When Benjamin was born, Penelope seemed like a giant. When he was a floppy 6-week-old infant, she was 4 and a half months old, well on her way toward being a real, solid, baby.
But then came walking. At a year, like the average kid, Benjamin got up and started toddling around. Not Penelope. By the time he was walking, she was fifteen months old and seemed to show no inclination. It is sometimes easy to ignore the way your children differ from the average, but walking was so visible, so salient. Plus, we saw Benjamin all the time, so it was hard to avoid comparisons.
At Penelope’s 15-month well-child visit, our very practical and pragmatic pediatrician, Dr. Li, told me not to worry that she wasn’t walking. “If she’s not walking by 18 months,” she said, “we’ll call in early intervention. But don’t worry! She’ll figure it out.” I did not have Dr. Li’s relaxed confidence or breadth of experience. I tried to explain to Penelope how to walk; she didn’t care. I tried to provide incentives, which were ineffective. You recall: She was a baby.
And then, about two weeks after the doctor visit, Penelope walked. Just like it was no big deal. Perhaps because she was so old by the time she learned, she never fell down much, either, just went from crawling around to walking normally in a day or two. And then I promptly forgot about my fear that she would never walk and moved on to other neuroses. (There are always more neuroses around the corner when you’re parenting.)
I don’t think my experience was unique. In the moment, physical milestones—sitting, crawling, walking, running—take on an outsize importance. You are in a whole new and bewildering world as a parent, and milestones seem like just about the only map of the territory. Correspondingly, failure to achieve these milestones at the time we expect tends to worry parents. I think part of the problem is that most discussions of this focus on the average age—as in, “Most children walk around one year.” This is true, but it misses the (perhaps surprising) fact that there is a very, very wide distribution in what is typical. (There’s a whole other conversation to be had about how we idealize “typical” in children, but that is for another day.)
To get a sense of this distribution, we can go to the data, collected from healthy, typically developing children. Specifically, we can use data collected and collated by the World Health Organization to look at not just the average age of walking (which is indeed around a year) but the whole distribution. The age range is visualized in the graph below. What we see from this is that the earliest walkers are around 8 months and the latest are close to 18 months. This is an astonishingly large range for parents to process. On a huge range of dimensions, an 8 month old is completely different from an 18 month old, and yet both are normal ages for first steps. That gives you some idea of how different children already are by this point, and it also gives you a sense of how you should view milestones: as a range.
The literature on development contains all sorts of other surprising facts about the wide ranges in physical milestones, most of them quite comforting. For example, a large share of children never crawl at all, or crawl in unusual ways. I’m guessing many a pediatrician has fielded questions from parents about why their child moves around like an inchworm through the house.
This is broadly reassuring, but you may also be left with the lingering question of whether any of this is predictive. If your child doesn’t walk until 17 months, is she doomed to be picked last on the kickball team? Working as I do with a number of highly accomplished economists, I feel a close kinship with this cohort. There is, in fact, very little evidence on the long-term impacts of late walking. Virtually all children—indeed, even the vast majority of those who are delayed beyond the normal range—do end up walking and running. If you ask, “Does early walking predict walking?” the answer will be, “No, everyone walks.”
Cribsheet: A Data-Driven Guide to Better, More Relaxed Parenting, From Birth to Preschool
By Emily Oster. Penguin Press.
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When it comes to being an elite athlete, the data is similarly thin. I don’t know if it’s just that researchers are not interested in predicting elite athletic performance. Perhaps the issue is that even if there were some relationship, the outcome is so unlikely, we’d never see it in the data. Making it to the Olympics, we find, is just not a realistic goal for most people.
So don’t be surprised if your child is a late walker, or a late crawler, or an early walker or a non-crawler. As with most issues in parenting, the key is not to panic when things don’t progress exactly as you expect.
