WELL-TO-DO parents fear two things: that their children will die in a freak accident, and that they will not get into Harvard. The first fear is wildly exaggerated. The second is not, but staying awake all night worrying about it will not help—and it will make you miserable.

Modern parents see risks that their own parents never considered. They put gates at the top of stairs, affix cushions to table corners and jam plastic guards into sockets to stop small fingers from getting electrocuted. Those guards are “potential choking hazards”, jests Lenore Skenazy, the author of “Free-Range Kids”. Ms Skenazy let her nine-year-old son ride the New York subway on his own. He was thrilled; but when she spoke about it on TV, a mob of worrywarts called her “America’s worst mom”.

Yet in fact American children are staggeringly safe. A kid under five in the 1950s was five times as likely to die (of disease, in an accident, etc) than the same kid today. The chance of a child being kidnapped and murdered by a stranger is a minuscule one in 1.5m.

What about academic success? Surely the possibility of getting into Harvard justifies any amount of driving junior from violin lesson to calculus tutor?

Bryan Caplan, an economist at George Mason University, says it does not. In “Selfish Reasons To Have More Kids”, he points to evidence that genes matter far more than parenting. A Minnesota study found that identical twins grow up to be similarly clever regardless of whether they are raised in the same household or in separate ones. Studies in Texas and Colorado found that children adopted by high-IQ families were no smarter than those adopted by average families. A Dutch study found that if you are smarter than 80% of the population, you should expect your identical twin raised in another home to be smarter than 76% but your adopted sibling to be average. Other twin and adopted studies find that genes have a huge influence on academic and financial success, while parenting has only a modest effect.

The crucial caveat is that adoptive parents have to pass stringent tests. So adoption studies typically compare nice middle-class homes with other nice middle-class homes; they tell you little about the effect of growing up in a poor or dysfunctional household.

The moral, for Mr Caplan, is that middle-class parents should relax a bit, cancel a violin class or two and let their kids play outside. “If your parenting style passes the laugh test, your kids will be fine,” he writes. He adds that if parents fretted less about each child, they might find it less daunting to have three instead of two. And that might make them happier in the long run. No 60-year-old ever wished for fewer grandchildren.

Does over-parenting hurt children? Probably not; but it exhausts parents. Hence the cascade of books with titles like “All Joy And No Fun” and “Go The F**k To Sleep”. Kids notice when their parents are overdoing it. Ellen Galinsky, a researcher, asked 1,000 kids what they would most like to change about their parents’ schedules. Few wanted more face time; the top wish was for mom and dad to be less tired and stressed.