Dalton Conley, a sociologist at NYU, argues against child-tax credits for large families in his book The Pecking Order and a column on Slate. His reasoning is interesting—beyond two kids, the middle children start to suffer from the shortage of parents’ time and money—though his chances of political success are scant, as he notes. I’ve yet to read his book, but I have seen plenty of evidence over the years that large broods are at least mildly disadvantageous for kids, all else being equal, despite the mythology of “big, happy families.”

Still, large broods are already quite rare nowadays. Since the peak of the baby boom average family size has fallen by half. Typical women have 1.8 children apiece over their lifetimes in the Northwest. In BC, the figure is currently under 1.4. Three-child families are still relatively commonplace, but four- and more-child families are rare.

And tax policy makes surprisingly little difference to how many children women choose to have. I have a justifiable reputation for wanting to change the tax system to help solve all manner of problems, but I’m skeptical about this idea. Poorer, less-educated women tend to have more children than richer, better-educated women. So per-child tax breaks are a progressive tax policy. Furthermore, poorer, less-educated women plan far fewer of their pregnancies than do richer, better-educated women. The point: accidents, not tax planning, boost family size.

The better leverage point on family size is not tax policy but reproductive health services and education: More than one third of births in the Northwest still result from unintended pregnancies, and the figure is above 80 percent for teen births.