"And the persistence of the change over time was striking. If you intervene at this critical time, when parents are trying to assign household roles for the first time, you establish more gender-neutral habits. And they stick."
Researchers have long argued that giving only mothers time off after the birth, adoption or fostering of a child reinforces the cultural belief that "mother knows best" when it comes to kids, and contributes to men spending more time at work, earning more and getting promoted more often - and women doing the bulk of the housework and child care.
The study found that, just as fathers who had taken leave under the daddy quota were spending a half-hour a day more at home, mothers were spending a half-hour a day less at home, and had increased their time at work by 9 per cent. Still, Patna said, mothers reorganised their time at home, spending less time on housework and more time on child care.
Canada gives mothers up to one year of unpaid, job-protected leave; for fathers, it gives 37 weeks that can become paid leave through an employment insurance program. Under this system, fewer than 20 per cent of Canadian fathers take leave. In 2006, Quebec increased the paid leave benefit from 55 per cent of take-home pay to 70 per cent, up to a maximum of US$767 a week, and established a five-week "daddy quota."
Although surveys show that millennial generation men, in particular, say they want to be more involved fathers than their own dads were, Patnaik said the size of the increase in those who took leave reflected more than a generational shift in fathers' attitudes.
"I identified an immediate jump between January 1, 2005, and January 1, 2006," she said.
"It's incredibly unlikely that everyone all of a sudden had egalitarian beliefs. But I do think the 'papa quota' made a difference. It sends the message that this is what we, as a society, think dads should be doing. This is what's normal."
Some 95 countries offer some form of paid parental leave to fathers, Patnaik said. And those with some of the highest rates of fathers taking parental leave have the "daddy-only" quota that Quebec instituted or other policies aimed at men. Great Britain is instituting a new policy this month to promote more shared leave between mothers and fathers. In Sweden, where 45 percent of fathers took paid parental leave in 2013, parents receive a financial bonus if they not only share the leave but also share the time equally.
In Iceland, mothers used to have long maternity leaves, and three years later, were still responsible for doing most of the child care. When the country adopted a "daddy days" quota, giving mothers and fathers three months of paid leave each, and three months for the family to share - nine months total - Iceland mandated that if fathers didn't use their three months, the family would lose the time.
Now, 90 per cent of fathers take paid leave in Iceland. And three years after the birth of a child, 70 per cent of the parents who lived together equally shared child care.
Schulte writes about Good-Life: work-life issues, time, productivity, gender and income inequality. She is the author of the best-selling Overwhelmed: Work, Love and Play when No One has Time.