The majority of Americans go without an essential employee perk, and it's costing them billions of dollars

Becoming a new parent is a huge undertaking, and for parents who are forced to take unpaid family leave, the situation becomes infinitely more challenging.

What's perhaps most frustrating is the abundance of research that often goes ignored, which illustrates how beneficial paid parental leave can be for not just parents, but also for children, society, and companies, too.

Luckily for some, there are companies taking note, including Netflix, The Bill & Melinda Gates Foundation, and Etsy, which offer generous paid parental leave policies.

But while extended paid leave for new parents is a hot trend for major companies, most people don't work in these companies or at the executive level, and currently about 21% of American companies offer paid maternity leave, according to the Society for Human Resource Management.

Under the Family and Medical Leave Act (FMLA) of 1993, qualifying American parents are guaranteed 12 weeks of family leave to care for a new child.

While the law requires companies with 50 or more employees to provide new parents with 12 weeks of leave, it doesn't require this leave to be paid. In fact, the US is one of just two countries in the world that doesn't ensure any paid time off for new moms, according to a report from the International Labor Organization. The other: Papua New Guinea.

The US's unpaid family leave is also restricted to full-time employees who have been with the company for more than a year, which, all told, applies to about 60% of workers in the US.

As a new study from the Center of American Progress illustrates, the lack of support for new parents in the US is costing families significantly.

According to its most recent analysis, working families in the US lose out on $20.6 billion in lost wages due to a lack of access to paid family and medical leave. This is in addition to the $8.3 billion in lost wages due to a lack of access to affordable child care.

As the report highlights, "these lost wages occur when individuals are forced to take unpaid leave, quit working, or reduce their work hours because they cannot access child care or paid leave." And their not just harming American families - these lost wages also take money away from local communities and the businesses that rely on consumer spending, the report notes.

The US Department of Agriculture finds that new parents spend, on average, about $70 a month for baby clothes and diapers and more than $120 a month on baby food and formula. And big-ticket items like furniture and medical expenses add up quickly. Without the guarantee of paid leave while caring for a child, many new parents are faced with the choice between economic hardship and returning to work prematurely.

According to a 2012 report from the US Department of Labor on family and medical leave, about 15% of people who were not paid or who received partial pay while on leave turned to public assistance for help. About 60% of workers who took this leave reported it was difficult making ends meet, and almost half reported they would have taken longer leave if more pay had been available.

"Support for motherhood shouldn't be a matter of luck; it should be a matter of course," YouTube CEO Susan Wojcicki wrote in an op-ed for the Wall Street Journal. "Paid maternity leave is good for mothers, families and business. America should have the good sense to join nearly every other country in providing it."

Wojcicki reported the rate at which new moms left Google fell by 50% when in 2007 it increased paid maternity leave from 12 weeks to 18 weeks. "Mothers were able to take the time they needed to bond with their babies and return to their jobs feeling confident and ready. And it's much better for Google's bottom line - to avoid costly turnover, and to retain the valued expertise, skills, and perspective of our employees who are mothers."

Andrew Bosworth, Facebook's vice president of the 600-person ads and pages team who welcomed his son Archer Americus in November 2014, previously told Business Insider that people often fear being away and losing traction, but in his experience the opposite effect happens after returning from parental leave.

"I'm probably doing better work in less time," he says. "I hear that repeated often among my peers and among my reports, which is nice. And I think there's some value there that's hard to capture."

In 2004, California became the first state to implement a paid-family-leave policy that enables most working Californians to receive 55% of their usual salary (up to $1,104) for a maximum of six weeks.

Since then, New Jersey and Rhode Island have actualized similar programs. The law enacting New York's family leave program will be phased in come January, 2018.

According to a report from the President's Council of Economic Advisers, more than 90% of employers affected by California's paid family-leave initiative reported either positive or no noticeable effect on profitability, turnover, and morale.

Another study, from the Center for Women and Work at Rutgers University, found that women who had taken advantage of New Jersey's paid-family-leave policy were far more likely than mothers who hadn't to be working nine to 12 months after the birth of their child.

The study also found these women to be 39% less likely to receive public assistance and 40% less likely to receive food stamps in the year following a child's birth compared to those who didn't take any leave.

A study of European leave policies by the University of North Carolina found that paid-leave programs can substantially reduce infant mortality rates and better a child's overall health.

And research out of The Institute for the Study of Labor (IZA) in Bonn indicates higher education, IQ, and income levels in adulthood for children of mothers who used maternity leave - the biggest effect comes for children from lower-educated households. The researchers cited this as a significant discussion for policymakers to have, as it could reduce the existing gap in education and income in the US.

There's plenty of evidence that supports the effectiveness of paid paternity leave, too.

A study by Boston College's Center for Work & Family found 86% of men surveyed said they wouldn't use paternity leave or parental leave unless they were paid at least 70% of their normal salaries.

But research out of Israel shows the more leave men take to care for children when they're young, the more the fathers undergo changes in the brain that make them better suited to parenting. And a study by two Columbia University Social Work professors found that fathers who take two or more weeks off after their child is born are more involved in their child's care nine months later. Simply put, paid paternity leave can help foster better father-child relationships.

And the more leave fathers take, the more mothers' incomes increase. In Sweden, where fathers must take at least two months off before the child is eight years old to receive the government benefits, researchers saw mothers' incomes increase almost 7% for every month of paternity leave their husbands took.

As President Barack Obama said during one of his weekly addresses in 2014, "Family leave, childcare, flexibility - these aren't frills. They're basic needs. They shouldn't be bonuses - they should be the bottom line."