Cribsheet

by Emily Oster

  Taking trash back in

  Roll bins back to their area

  Recycling goes in first, closest to garage

  Then trash goes

  Put some diatomaceous earth in trash and recycling

  Put some baking soda if there is an odor

  Put a new bin liner (in mud room closet) in trash (not in recycling)

  Then congratulations you are done!

  Apparently, due to some maggot and fly issues (I have a problem with bugs, but also tend to do things that attract them, like failing to fully close the garbage bags), he had adopted a many-step system involving something called “diatomaceous earth” to keep things dry and bug-free.

  I was sorry to have to do this at all, but it made me a lot more grateful for the 99 percent of Mondays that he does it.

  The Bottom Line

  Marital satisfaction does decline, on average, after children.

  These declines are smaller and briefer if you’re happier before children, and if the kids are planned.

  Unequal division of labor and less sex probably do play some role, although it is hard to get a sense of how important these are.

  There is some small-scale evidence suggesting marital counseling and “marriage checkup” programs can improve happiness.

  20

  Expansions

  Some people have told me they are ready for another baby on leaving the delivery room. Others take years before reluctantly wanting to try again. Some never want another kid. Some people plan out the child timing precisely—down to the month. Others adopt more of a wait-and-see approach.

  This chapter is about the choice of whether to have more than one child, and, if you decide to have another child, the choice of timing. Is there an “optimal” number of children? Or an ideal spacing between them?

  Spoiler alert: There isn’t much of a science-based answer to these questions. Any small impacts are likely to be dramatically outweighed by the most important consideration, which is what works for your family.

  For example, if you have your first child at thirty-eight and you want three kids, you’ll likely have to have them pretty quickly. If you’re a doctor and you are planning your kids around residency, this will tell you your timing. And, of course, things change. You do not always get pregnant when you want to. Due to a lack of maternity leave, my mom attempted to time my brother to arrive over Christmas break, but she got January 11 instead.

  Sometimes life intervenes. I thought we’d have our kids closer in age—more like three years apart, rather than four. But then I had a big, and unexpected, professional setback right around when we’d need to start working on number two. I was barely in emotional shape to parent one kid, never mind have another. So we waited.

  The choice of how many children to have is even more personal. Does your family feel done with just one? Do you want another? And, of course, sometimes it’s hard to have a second child, and sometimes it’s an accident.

  All this is to say that the data has very little to add to your family preferences. But we can visit the data there is, first on the question of number of children, and then—conditional on the number—the question of birth spacing.

  NUMBER OF CHILDREN

  Economists are very interested in number of children and, beginning with Gary Becker’s influential work, in the “quantity-quality” trade-off. The idea here is that parents face a tension between number and quality of kids. If you have more kids, then you cannot invest as much in each of them, so they’ll be “lower quality.”

  By “quality,” we tend to mean things like school attainment—the “investments” you make as a parent are in your child’s education, IQ, etc. Let no one tell you economists are not clinical about their discussions of parenting.

  Much of the economic writing about this focuses on understanding what is called the “demographic transition”—the movement of countries as they develop from very high fertility rates (think: six to eight kids) to lower (two or three). The idea is that as your country gets richer, you might want to focus on quality of children rather than quantity, and this would drive some of these fertility declines.

  The basic theory that there is a quantity-quality trade-off would imply that if you have more kids, they will do worse in terms of human capital—less education, maybe lower IQ. But this is just a theory—what does the data say?

  As with most things in the book, this is difficult to test, since the kinds of parents who have many children differ from those who have few. But some researchers have done this, generally using a method with “surprise” births. They look at the arrival of twins as something that increases the size of the family while not affecting the number of children you actually wanted.1

  The results from the best of these papers generally show that the number of children plays a relatively little role in determining schooling or IQ.2 They do find that birth order matters. Later-born children tend to do (slightly) worse on IQ tests and get less schooling than their earlier-born siblings. This may be due to parents having less time and resources to devote to them. But it’s not the number of children that drives the association. A firstborn child with two siblings seems to do the same as a firstborn child with one.3

  A second question people (typically not economists) often ask is whether there is some downside to having an only child—will they be socially awkward?

  Again, this is hard to study, given the differences across families. To the extent that we have evidence, this concern seems unfounded. One review article, which summarizes 140 studies on this broad question, found some evidence of more “academic motivation” among only children, but no differences in personality traits like extroversion.4 Even this fact about academic motivation may be more about birth order—firstborn children score higher on this regardless of whether they have siblings—than about being an only child.

  Based on such paltry data, it is hard to say with confidence that it doesn’t matter how many children you have. And your kids’ relationships with their siblings (if you choose to have them) will define many things about them—for good and for ill. But there isn’t anything in the data that would tell you one choice is necessarily better than another.

  BIRTH SPACING

  So let’s say you decide you want to have another kid. Does the data tell you when you should do it?

  Again, no, not really. To the extent research has been done on “optimal birth spacing,” it tends to focus on two things: the relationship between birth spacing and infant health, and the relationship between birth spacing and long-term outcomes like school performance and IQ.

  Most of the discussion focuses on distinguishing more typical birth intervals (say, two to four years apart) from very short ones (less than eighteen months) or very long (more than five years). However, regardless of the outcome you are studying, this is a challenging data problem. The issue is that both very short and very long intervals are unusual.

  Some people do plan to have two children very close together in age, but relative to other birth intervals, babies born within a year of each other are less likely to be planned. Unplanned births may have different outcomes than planned ones, even putting aside spacing. On the flip side, very long spacing between children is also somewhat unusual. It is more likely—not certain, but more likely—that families with very long birth spacing struggled with fertility challenges. This could matter as well, especially when we look at infant health.

  For these reasons, we want to take most of the evidence with a grain—or, really, a big handful—of salt.

  Infant Health

  Studies of infant health and birth spacing tend to focus on outcomes that can be measured at birth: for example, is the child premature, low birth weight, or small for gestational age? Correlational studies have shown links between both short birth
intervals and long birth intervals and all these outcomes. For example, in a 2017 study of almost 200,000 births in Canada, researchers found that there was an 83 percent increase in the risk of preterm birth for women who got pregnant within six months of their last birth.5

  These large effects also show up in other studies—one in California and another in the Netherlands—that focused on recurrence of preterm birth (i.e., the analysis was limited to women who had already had a preterm birth).6

  This very large effect is not, however, replicated everywhere, and there is a question of whether it might be driven by differences across moms. This concern is at least somewhat validated by a study in Sweden that was able to compare women to other women—siblings or cousins—in their family. This addresses the concern that some family-level differences are driving the results.

  In comparing siblings, they were effectively asking whether two children born to the same mother have different outcomes depending on the birth interval. To the extent that we worry that some mothers differ from others, this addressed that concern.7

  These Swedish researchers replicated the finding that very short birth intervals increase prematurity when they compared across families, but they found much smaller effects (more like 20 percent than 80 percent) when they compared siblings. The effects when comparing cousins were somewhere in the middle. They found no association between these short intervals and low birth weight or other outcomes once they compared siblings.

  Although there is a lively debate about which set of numbers to believe, I think there is a good argument in favor of the sibling comparisons, which would suggest that although there is some elevated risk of prematurity with very short spacing, it is not very large.

  This Swedish study does find that very long intervals—here defined as more than five years between birth and the next pregnancy—are associated with worse outcomes. And we see some similar evidence in the Canadian work. However, very long intervals between births are unusual, and more likely to be associated with older mothers or fertility problems. It is not clear how much we want to learn from this about choosing longer intervals.

  Long-Run Outcomes

  Infant health is important but short term. Are there any long-run consequences for children related to birth spacing? Are test scores lower for children whose siblings are close in age?

  This analysis is challenging since people choose their birth spacing, to some degree. But at least one study tried to compare women who intended to have babies at the same time but ended up having them at different times (for example, due to miscarriage).8

  When researchers performed this analysis, they found that for the older child, test scores were higher if there was more space between that child and their younger sibling. This may reflect, for example, more parental time invested in reading or other skill development at young ages. These effects, though, were pretty small.

  For these younger children, at times concerns have been raised about links between short birth spacing and autism.9 Although multiple studies of this do show some links, they are not able to adjust as well for differences across families, so this evidence remains suggestive.

  Overall, what do we take from all this? I would argue that any links there are are not consistent or large enough to outweigh the preferences that you are likely to have.

  To the extent that you have no preferences at all about this, I think the bulk of the evidence suggests there are some small risks—both short and possibly long term—to very short birth intervals. So waiting until the first child is at least a year old to get pregnant again may be a good idea. It also just may be easier on you as a parent, given the intensity of the infant stage.

  The Bottom Line

  The data doesn’t provide much guidance about the ideal number of children or birth interval between them.

  There may be some risks to very short intervals, including preterm birth and (possibly) higher rates of autism.

  21

  Growing Up and Letting Go

  When Penelope was almost three and we were thinking about having a second kid, Jesse and I were also in the job market, looking for two faculty jobs together. We went to Michigan, where we were invited to the house of two slightly older economists whose children were fifteen and eighteen. The conversation about economics exhausted, we turned to talking about our kids.

  “The thing is,” one of them told us, “when our kids were four and one, we used to look at each other and say, ‘I can’t wait until they are in high school and everything will be easy.’ Then finally, last year, they were both in high school, and what we learned is that there is no problem that cannot be solved with a four-hour discussion every night about the minute details of high-school social life.”

  When you’re in the thick of it with very early parenting—with the exhaustion and uncertainty of it all—there is the promise in the distance of a time when your child will use the bathroom on their own, put on their own jacket, and eat with a fork. And it is definitely true that the first time my son came out of the bathroom and said he had peed on his own, I did a little jig.

  But there is a flip side. Little kids mean mostly little problems. As your kid gets bigger, the number of things you worry about goes down, but they get more important. Is my kid achieving academically? Are they fitting in socially? Most important, are they happy?

  Part of what makes this hard, especially for someone like me, is that the problems get more varied as kids get older, and much less amenable to data analysis. Sure, you can look at some data about whether the “new math” is better than the “old math,” but how to get a child to engage socially, and whether that even matters, is largely beyond the realm of easy empirical analysis. We have to grope forward, ideally listening to our kids to see what works for them—if it takes a four-hour conversation, we’ll clear our schedules.

  We keep at it, in part because the rewards are correspondingly so much bigger. Seeing your kid do well at something they love, seeing them excited about learning something new, watching them work through a challenge—there is nothing better. And you do not need data to tell you that. So just remember that while there will always be parenting challenges, there are many joys on the horizon, too.

  As hard as it is to believe when you’re staring down preschool, your parenting adventure is still just beginning. But you certainly know more than you did back in the delivery room. Progress!

  You know that early parenting is full of advice. This book, it’s full of advice (or at least decision processes). As I finished writing, I therefore thought about the question, What is the best parenting advice I’ve ever gotten?

  Here it is.

  When Penelope was two, we planned a vacation in France with some friends. We had been to the location before and I knew there were lots of bees.

  At our two-year-old well-child visit, I therefore had a set of questions for Dr. Li.

  “Here’s what I’m worried about. We are going on this vacation, and there are bees. It’s kind of isolated. What if Penelope is stung? She’s never been stung before. What if she’s allergic? How will I get her to a doctor in time? Should I bring something to be prepared for this? Should we test her in advance? Do I need an EpiPen?”

  Dr. Li paused. She looked at me. And then she said, very calmly:

  “Hmm. I’d probably just try not to think about that.”

  And that’s it. “Just try not to think about that.” She was right, obviously. I had built up this elaborate and incredibly unlikely scenario in my head. Yes, this could all happen. But so could a million other things. Parenting cannot be about thinking about every possible eventuality, every possible misstep. Sometimes, you just need to let it go.

  So, yes, it makes sense to take parenting seriously, and to want to make the best choices for your kid and the best choices for you. But there will be many times that you need to just trust that if you’re doi
ng your best, that’s all you can do. Being present and happy with your kids is more important than, say, worrying about bees.

  At the end, let’s raise a glass to using data where it’s useful, to making the right decisions for our families, to doing our best, and—sometimes—to just trying not to think about it.

  ACKNOWLEDGMENTS

  Thank you, first, to my wonderful agent, Suzanne Gluck, and my amazing editor, Ginny Smith. Without you two this definitely would not have gotten off the ground or finished. I am grateful to Ann Godoff and the whole team at Penguin for being willing to go around with me again on this book, and for supporting my first one so wonderfully.

  Adam Davis was an incredible and patient medical editor. The book would not have come together without his advice and guidance.

  Charles Wood, Dawn Li, Lauren Ward, and Ashley Larkin also provided invaluable medical commentary.

  Emilia Ruzicka and Sven Ostertag contributed excellent graphical design. Xana Zhang, Ruby Steele, Lauren To, and Geoffrey Kocks provided invaluable research assistance, from literature reviews and fact checking to proofreading and paper collation.

  In conception, this book benefited hugely from idea generation from many people. From the Brooklyn focus group: Meghan Weidl, Meriwether Schas, Emily Byne, Rhiannon Gulick, Hannah Gladstein, Marisa Robertson-Textor, Jax Zummo, Salma Abdelnour, Melissa Wells, Laura Ball, Lena Berger, Emily Hoch, Brooke Lewis, Alexandra Sowa, Barin Porzar, Rachel Friedman, Rebecca Youngerman, and especially Lesley Duval. And from everyone on Twitter, and the Academic Moms on Facebook.