New York state just passed the nation's most comprehensive paid family leave policy yet, guaranteeing that all New Yorkers — men and women, employees of small and large firms, and full-time or part-time employees — can take three months of partially paid time off to take care of a new child or a sick family member without losing their jobs.

New York will join California, New Jersey, and Rhode Island in guaranteeing paid family leave. But New York's benefits will be much more generous — offering 12 weeks while California and New Jersey offer six, and Rhode Island just four. (It's still not as generous as Washington, DC's 16-week proposal, which hasn't passed yet but is looking likely to.)

New York's plan uses a popular model in working as insurance, funded by small paycheck contributions (about a dollar per week) from employees. Bosses won't have to chip in, nor will taxpayers.

The policy will also be phased in gradually — starting off at 8 weeks and 50 percent of pay in 2018, and reaching 12 weeks and 67 percent of pay in 2021.

"This is history in the making," said Debra Ness, president of the National Partnership for Women and Families, in a statement. Ness said the policy will benefit 6.4 million New York workers who aren't guaranteed paid time off, and is "a huge and meaningful victory for workers and their families."

Having paid leave is in fact a huge deal for most working families, especially low-income ones. Just 12 percent of American workers have access to paid family leave through their employer, and that access is unequally distributed — 5 percent of workers in the lowest-paid 25 percent of the workforce have it, while 22 percent of the top 10 percent of earners do.

An investigation by In These Times found that one in four working mothers goes back to work within two weeks of childbirth, usually due to financial pressures. But going back to work so soon can have nightmarish consequences for a new mother's physical and mental health. Lacking paid leave also pushes a lot of women out of the job market and discourages fathers from being equal partners in child-rearing.

New York's law is a major sign of momentum for paid family leave

In the same budget bill as family leave, New York legislators also passed a $15 minimum wage increase like California's. It may not seem like a surprise that blue-state New York would pass these progressive policies, but it's actually been a hard-fought battle.

Gov. Andrew Cuomo is a very pro-business, centrist Democrat. Just last year, Cuomo said that a $13 minimum wage in New York City was a "non-starter," and that he and the legislature lacked the "appetite" to pass paid family leave. The New York Senate is also Republican-dominated, and the party hasn't been warm to either minimum wage hikes or paid family leave.

But a lot has changed over the last year. Since Cuomo's father passed away and his partner Sandra Lee got breast cancer, he's been much more outspoken about the importance of family leave.

Cuomo has also had to contend with energized challenges from the left in the form of the Working Families Party — which made Cuomo's 2014 re-election rockier than expected when it recruited left-flank challenger Zephyr Teachout before ultimately endorsing Cuomo — as well as the substantial populist energy around the 2016 election.

"In the past year, all of the Democratic presidential candidates have made paid family leave a top priority issue, and the rise of Bernie Sanders has validated progressive politics in America as a major force," said Bill Lipton, founder of the Working Families Party. "And I think politicians of all stripes have to contend with this new reality."

Lipton noted that paid family leave is extremely popular among New Yorkers, including 77 percent support among people living in the suburbs and 69 percent among Republicans. "Senate Republicans knew that opposing such a popular program would hurt them big-time on election day, and they came around," he said.

Paid family leave, minimum wage increases, and other progressive economic policies have experienced a surge of national interest and grassroots advocacy over the last several years, and New York, home of the "Fight for 15" movement for a $15 minimum wage, has often been at the center of it.

"New York is part of a growing, national movement to advance progressive workplace policies like paid family leave, equal pay, earned sick days, affordable childcare and fair scheduling," said Lisa Guide from the Rockefeller Family Fund, one of the largest funders of workplace policy reform in the country. "We can correct inequality in our lifetime by making policies like this one the norm rather than the exception."

Moreover, as Rebecca Traister notes at The Cut, the popularity of paid family leave is fueled by a growing understanding that everyone benefits from it, not just women:

It seems worth noting that an issue that has been considered third-rail-feminist radicalism for decades, so improbable when it is described as "maternity leave" that we wave it off as a pipe dream, can gain steam when political men — Barack Obama, Andrew Cuomo, Joe Biden — put their brawn behind it, and begin to describe the ways in which men might benefit. It’s key to understanding how "women’s issues" can become, simply, issues.

The US doesn't have national paid leave, so some states and businesses have to try to fill in the gaps

A lot of Silicon Valley companies and other white-collar employers have been aggressively competing to make their parental leave programs more generous over the past few years. But for Americans who don't happen to work at companies like these, things can be tough.

The United States does have an unpaid 12-week national family leave policy, but its protections are meaningless for a large chunk of the population. About 40 percent of workers aren't covered under the Family and Medical Leave Act because their company has fewer than 50 employees, or because they've worked too few hours or been there less than a year. And of course, many people just can't afford to take unpaid time off of work.

Our lack of national paid leave puts us starkly at odds with the rest of the developed world, and even the developing one.

Democrats in Congress have been trying to fix this by pushing the FAMILY Act (Family and Medical Insurance Leave Act), which Vox's Matt Yglesias called the "best parental leave proposal in Congress today." It's pretty similar to New York's plan, an insurance model with 12 weeks of leave at two-thirds of pay, except it's funded with paycheck contributions from both employers and employees. Republicans in Congress, unsurprisingly, have been unwilling to even give the bill a hearing.

But 12 weeks is actually a low bar compared with what other developed nations offer: 35 weeks in Canada, 44 weeks in Germany, 70 weeks in Norway. Even Saudi Arabia offers 10 weeks of paid maternity leave, which is a lot more than the zero weeks Americans get unless they work for a generous employer.

Update: This piece was updated to clarify the Working Families Party's role in the 2014 governor's election.