ALONG with its Nordic neighbours, Sweden features near the top of most gender-equality rankings. The World Economic Forum rates it as having one of the narrowest gender gaps in the world. But Sweden is not only a good place to be a woman: it also appears to be an idyll for new dads. Close to 90% of Swedish fathers take paternity leave. In 2013, some 340,000 dads took a total of 12 million days' leave, equivalent to about seven weeks each. Women take even more leave days to spend time with their children, but the gap is shrinking. Why do Swedish dads take so much time off work to raise their children?

Forty years ago Sweden became the first country in the world to introduce a gender-neutral paid parental-leave allowance. This involves paying 90% of wages for 180 days per child, and parents were free to divvy up the days between them in whatever way they pleased. But the policy was hardly a hit with dads: in the scheme's first year men took only 0.5% of all paid parental leave.

Now they take a quarter of it. One reason is that the scheme has become more generous, with the number of paid leave days for the first child being bumped up from 180 to 480. But it has also been tweaked to encourage a more equal sharing of the allowance. In 1995 the first so-called "daddy month" was introduced. Under this reform, families in which each parent took at least one month of leave received an additional month to add to their total allowance. The policy was expanded in 2002 so that if the mother and father each took at least two months' leave, the family would get two extra months. Some politicians now want to go further, proposing that the current system of shared leave be turned into one of individual entitlements, under which mothers should be allowed to take only half of the family's total allowance, with the rest reserved for fathers.

Policies similar to the Swedish "daddy months" have been introduced in other countries. Germany amended its parental-leave scheme in 2007 along Swedish lines, and within two years the share of fathers who took paid leave jumped from 3% to over 20%. One of the most powerful arguments in favour of splitting parental leave more equally is that it has positive ripple effects for women. After Swedish men started to take more responsibility for child-rearing, women have seen both their incomes and levels of self-reported happiness increase. Paying dads to change nappies and hang out at playgrounds, in other words, seems to benefit the whole family.