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A new study (PDF here) by University of Notre Dame economist Kasey Buckles and graduate student Elizabeth Munnich finds that siblings spaced more than two years apart have higher reading and math scores than children born closer together. The positive effects were seen only in older siblings, not in younger ones.
The authors attribute at least part of the difference to older children getting more of their parents’ time during the first formative years of their lives before a younger sibling comes along. The paper is set to be published in an upcoming issue of the Journal of Human Resources.
Here’s the abstract:
This paper investigates the effect of the age difference between siblings (spacing) on educational achievement. We use a sample of women from the 1979 NLSY, matched to reading and math scores for their children from the NLSY79 Children and Young Adults Survey. OLS results suggest that greater spacing is positively associated with test scores for older siblings, but not for younger siblings. However, because we are concerned that spacing may be correlated with unobservable characteristics, we also use an instrumental variables strategy that exploits variation in spacing driven by miscarriages that occur between two live births. The IV results indicate that a one-year increase in spacing increases test scores for older siblings by about 0.17 standard deviations—an effect comparable to estimates of the effect of birth order. Especially close spacing (less than two years) decreases scores by 0.65 SD. These results are larger than the OLS estimates, suggesting that estimates that fail to account for the endogeneity of spacing may understate its benefits. For younger siblings, there appears to be no causal impact of spacing on test scores.
The paper fills in one of the few remaining gaps in the large body of economic research that’s been done on family structure and children’s outcomes. We already know that children from larger families generally have lower educational attainment and IQ scores, worse employment outcomes, and are more likely to engage in risky behavior. But birth spacing has received less attention.
The authors sampled a nationally representative panel of 12,686 young people ages 14 to 22 in 1979 and their children, and used the Peabody Individual Achievement Tests for math and reading to measure performance. The largest effect they observed suggested that a one-year increase in spacing improves reading scores for older children by 0.17 SD—which would be three times the effect of increasing annual family income by $1,000.
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to be fair to the authors miscarriage is quite a good way of controlling (admittedly not completely randomly) for spacing. it shows people wanted to space children less and were involuntary given a larger than desired gap between children.
the problem i see is that miscarriage is likely to be a significant event for the family that has effects of its own on children and parents.
it isn’t surprising that spending time with your children is good for the children. it is however surprisingly hard to demonstrate that it is causal rather than due to parent education.
It sounds like they haven’t considered the effects that the kids have directly on each other. (I’ll bet that none of the authors have personal experience with large families.)
Okay: We all say that the best way to learn something is to teach it, right?
And what does a typical preschooler do? He spends some time “teaching” the baby.
This is often “unimportant” stuff, like “teaching” the baby to laugh, but it’s hugely important from the perspective of cognitive development. To “teach” the baby to laugh, you have to formulate a plan, choose when to implement it, notice the reaction, evaluate whether it worked, and either refine your plan (perhaps incorporating information from other sources) or repeat it (“practice” the skill).
You additionally have to sort out confounding factors: Did the baby ignore me when I did my trick because she’s busy or almost asleep? Did she cry rather than laugh because I startled her or because she’s hungry or needs something? In other words, does a one-time failure mean that my trick doesn’t work at all, or does it mean that I need to improve my timing?
This is fundamentally the same skill set that stand-up comedians struggle with (and anyone asking for a pay raise). Of course spending even a few minutes most days doing this “unimportant” but highly complex cognitive task is going to improve these kids’ mental abilities.
this effect can be more dire in poor countries- there is an African word “kwashiokor” which denotes a type of malnutrition that an older sibling gets when a younger is born- it is due to a decrease in breast milk intake that the older suffers relative to when there is no sibling
Parents have no lasting effect on how kids turn out.
So this article and any other articles putting nurturing assumptions as basis are false.
Read “Nurturer’s Assumption” by Judith Rich Harris.
Would be interesting to see a study that compared the achievement of only children with the oldest child in multi-child households to discern what happens if that second sibling never comes along? Wonder if there is a spacing for that second sibling where the achievement of the eldest child is equal to that of an only child (i.e., there ceases to be a disadvantage to having younger siblings and perhaps even a developmental advantage).
Another research that confuses correlation with causality. If kids born within a close gap of each other are less smarter, I wonder what happens to twins or triplets.
It is more to do with how much time parents spend with their kids, how much they focus on the child’s development and also on how smart the parents themselves are.
And parents who are smart themselves and also spend a lot of time with their kids, teaching them math, reading, etc. and in general, investing time in their kids are more likely to have less kids who are more spaced out!