Facebook founder Mark Zuckerberg may have taken an extended paternity leave after the birth of his daughter, but generally, American men do not take more than a few days. Ninety-six percent of American men are back to work within two weeks of a baby's birth.
"There might be some stigma attached," says Gordon Dahl, an economist at the University of California, San Diego. " 'What if I take paternity leave, will I not get the next promotion? Or will people think I'm not as connected to the workplace? Am I kind of signaling that I don't care about work enough?' "
Dahl studied leave policies in Norway, where a generation ago men took long paternity leave at the same rate as American men. Then, in 1993, Norway changed the law. After every birth, working parents still got eight months of paid leave to split among themselves, but four weeks were added just for dad.
"Overnight, paternity leave take-up went from about 3 percent to 35 percent of fathers," Dahl says.
It was a nice boost, mostly among men working union and government jobs.
What puzzled Dahl was the change that he saw over the next two decades. "This is where the story gets more interesting, because over time, it gradually crept up to about 70 percent of fathers taking leave," Dahl says.
He found the secret was seeing a dad come back to his job, especially in the private sector, without any problems.
"If you had a co-worker take leave, then you're 11 percentage points more likely to take leave yourself when you have your child. If you have a brother who took leave, you're 15 percentage points more likely to take leave," Dahl says. "These are not small effects. These are big increases in how many people are willing to take leave."
Something similar may be brewing in California, where paid leave has been available to working parents since 2004. Consider Facebook. A combination of factors is tipping the culture there toward men actually taking their paternity leave.
Tom Stocky, a vice president, had a daughter in 2012 and took the full four months that Facebook offers new parents. "Most of my friends were really surprised and had a lot of questions about what happened when you were away, and what did the rest of your team do, and things like that," Stocky says.
Three years later, Stocky believes the leave he took is having a big impact. The men he manages are much more likely to inquire about and take a long leave.
"I probably meet with a new dad every month or two. And it seems like there's kind of a peer group now that is encouraging and supporting each other, and more people are taking it now as a result," Stocky says.
Among them is Tom Whitnah, an engineering manager at Facebook. "I saw Tom Stocky taking his leave right as I joined the search team, and it just was really clear that it was something that he thought was really important," Whitnah says.
Whitnah's two kids arrived 17 months apart, and he took full leave with each one.
"I had just become a new manager, and I felt like I wasn't sure how a team goes without their manager for one or for three months, and he made it really clear this is something that we accommodate. Just made me feel so much less nervous," he says.
The number of California dads taking a break from work to spend time with a new child is beginning to pick up. Seventeen percent of men in California took leave the first year it was offered; 26 percent did five years later.
Stocky is now taking another long parental leave. He begins three months of caring full time for his son, at the same time that his boss, Mark Zuckerberg, comes back to work from paternity leave.
Does what happens at Facebook have anything to do with the rest of the country? Maybe. But if there's one thing that the folks at Facebook understand, it's the power of friends.