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IN THE EARLY American women of the 1970s gave birth to an average of 2.12 children each. In 2018 that figure had dropped to 1.73. Many alterations in people’s lives have been invoked to help explain this change, including the fact that women are now better educated, more likely to have a job or run businesses, and have better access to contraception than their antecedents of five decades ago. Furthermore, the demand for children to work as extra pairs of hands on family farms has decreased.
None of these explanations, however, overlap perfectly with the birth rate curves. Other factors must also be present. And Jordan Nickerson and David Solomon, finance professors at Massachusetts Institute of Technology and Boston College, respectively, think they’ve found one intriguingly counterintuitive: America’s increasingly protective laws on child car seats.
Their study, “Car Seats as Contraception”, published in SSRN, an archive for so-called prepress documents that have yet to undergo formal peer review, examines the effect that car seat policies may have had on American birth rates between 1973 and 2017. During the Reagan era , only really very young children age under three – they normally had to be secured in child seats. But state governments have gradually increased the requirements since then. Today, most places in America seat children in safety seats until their eighth birthday. This concern for the safety of young people has had the unintended consequence, Dr. Nickerson and Dr. Solomon suggest, of fewer families of three children.
In drawing this conclusion, they correlated census data with changes in state safety seat laws. They found that tightening those laws had no detectable effect on first and second child birth rates, but was accompanied by a drop, on average, of 0.73 percentage points in the number of women giving birth to a third. while the first two were young enough to need safety seats. That might not sound like much, but it’s a significant fraction of 9.36% of the women in the sample who became mothers for the third time.
The authors also made two other pertinent observations. The reduction they saw was limited to families who actually had access to a car. And it was bigger in families where a man lived with his mother. This last point is relevant, they think, because this man would take up space in a vehicle that might otherwise be occupied by a child.
And the space in the vehicle is the crucial factor. Back in the days of preparing the safety seat, squeezing three small children into the back of a family saloon was a perfectly feasible proposition. Most of these cars, however, can only comfortably accommodate two safety seats. So, the older a child has to be before a safety seat is not required, the longer a family has to wait before a third child can get into the car. Sometimes, that wait will mean that no third child will ever be conceived and born.
Unless, of course, the affected family buys a larger car. And here things get even more interesting, for the obvious reasons not to – big cars cost more and are more expensive to run – it may not be the only disincentive to change. Dr. Nickerson and Dr. Solomon have found, in fact, that the deterrent to the third child seems stronger among the wealthiest families. As they note, “large cars like minivans also have classy and aesthetic connotations that can make people reluctant to change even when they can afford it.”
Rear seat driver
Strangely, however, the authors do not leave it like this. Instead, they refer to previous studies that suggest that, for children over the age of two, safety seats are no better than seat belts to protect against death or serious injury in an accident. They estimate that laws requiring children to sit in special seats until the age of eight saved about 57 lives in 2017 and contrast that number with the 8,000 children who could have been conceived and born in the absence of such rules. There is, they conclude, no “compelling social interest” in requiring child seats for children over the age of four.
This seems odd. The comparison between allegedly lost lives and actual saved lives is, to put it politely, a strange moral calculation. And the empirical basis for this is, in any case, questionable. Alisa Baer, a New York-based pediatrician specializing in car seat safety and who claims to have installed at least 15,000 such car seats over the years (she is known as “The Car Seat Lady”), says this part of the document it is “completely absurd”. Infant car seats, he says, “save the quality of life” of children who would suffer higher injury rates than simply buckling up, including massive abdominal trauma and paralysis. A recent study by Mark Anderson at the University of Washington and Sina Sandholt at Columbia University confirms this point.
This, however, does not detract from the broader observation that Dr. Nickerson and Dr. Solomon make that well-intentioned actions can have surprising ripple effects. And one of them, it seems, is that the rear seats of American cars, once renowned as places where children were conceived, can now, themselves, act as contraceptives.■
This article appeared in the Science and Technology section of the print edition under the title “Mooring Control”
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