WHY subsidise childcare? The most commonly-heard justification is that doing so will encourage work. Child care is hugely expensive, to the point where it is often better for parents—overwhelmingly, mothers—to look after a child themselves rather than work. “Gender is no longer the factor creating the greatest wage discrepancy in this country, motherhood is”, said Ivanka Trump at the Republican convention, announcing that her father, like Hillary Clinton, would propose a child care-subsidy plan. That plan emerged on September 13th. At first pass, the economic argument for subsidising child care is a bit iffy. If a mothers’ potential wages reflect her productivity, and if the price of child care reflects the costs of providing it, then there is no economic loss when a mother chooses to stay at home. Take a simplified example: suppose a low-skilled worker can either take a minimum-wage job in Walmart while paying another minimum-wage worker to look after her child, or she can stay at home and care for the child herself. If she stays at home, the second minimum-wage worker takes the Walmart job. Whatever she decides, someone looks after the child, and someone works at Walmart. There is no economic gain from switching the workers around. Even if the woman is high-skilled, making work more lucrative than saving on child care costs, the gap between her wages and the price of child care reflects the benefit to the economy of her choosing to work. She is sufficiently incentivized without any government intervention.

Of course, economic reality is more complicated. Mothers may not fully account for the effect a break from work might have on their future wages. And there are other benefits to reducing the costs of having children, not least that kids grow up to work and pay taxes themselves (see article).

But why not simply subsidize parenthood more—for example with a bigger child tax credit? Parents could always spend the extra money on child care if they so wished. The main effect of singling-out child care is social. If gender norms coerce mothers, rather than fathers, into staying at home, then a child-care subsidy would be liberating. This paternalistic (or perhaps maternalistic) view says that women are making bad choices that need fixing with financial incentives.

Suppose that is what we want to achieve. Hillary Clinton’s plan is more effective than Donald Trump’s. First, it is simply more generous. Mrs Clinton promises that no household will have to pay more than 10% of their income in child care. She is a little vague about how exactly she will achieve this. But were a Clinton administration simply to pay for costs exceeding 10% of income, many families, especially poor ones, could find the government footing the bulk of their child-care bills. Ten per cent of median income is about $5,700, while the average cost of child care for an infant is $12,000 a year (though it varies dramatically with geography, in part because richer parents demand fancier care).

By contrast, Mr Trump would let families deduct the cost of child care from their taxes, up to its average cost of child care in their area. This is much less generous to the poor, whose low rate of income-tax means they benefit less from tax-deductions. However, it could be somewhat more efficient. Were Mrs Clinton to cap child-care costs, consumers might be tempted to buy pricier care (Mr Trump’s plan would also encourage more spending, but less dramatically). And capping costs a 10% of income means increasing implicit tax rates by 10 percentage points, because for every dollar earn, you lose ten cents of your subsidy.

More fundamentally, however, Mr Trump’s plan would not encourage work over stay-at-home parenting. That’s because he promises to “ensure stay-at-home parents will receive the same tax deduction as working parents”. If mothers get the benefit whether they go to work or buy child care, their incentives do not change. There would be no countervailing nudge against gender norms. Mr Trump’s policy is really to subsidise parenthood, not child care.