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Women might not earn as much as men for the same job, but there is one area where they come out ahead: paid parental leave. A new study by the Society for Human Resource Management found that the average amount of maternity leave women get is 41 days, compared with 22 days of paternity leave, on average, for men.

SHRM found that paid adoption leave falls in the middle, with an average of 31 days. Other types of paid time off including vacation, personal, and sick days are generally accrued based on tenure, with average paid vacation allotments ranging from eight to 22 days.

Even on the low end, these leave numbers might be considered generous, seeing as how the United States is the only one of 41 developed countries that doesn't mandate paid parental leave, a recent Pew Research Center study found.

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Unfortunately, even this "good" news has a dark side that ultimately makes it tougher for women to advance in the workplace, said SHRM director of workforce analytics Evren Esen. “The imbalance in parental leave indicates that organizations still expect mothers to take on the majority of care for a new child... [which] may discourage fathers from taking a similar amount of time off to care for a new child,” she said in a statement.

An article last year in the Harvard Business Review came to the same conclusion, saying that targeting maternity leave, even when it's generous, to mothers only feeds into a 1970s-era idea. "The challenge for women is that this reinforces stereotypical gender roles: women are mothers, and men are workers," it warned.

The good news is there are signs that some more egalitarian companies are bucking the trend, being more generous with parental leave and making it available for both parents. Yogurt manufacturer Chobani, for instance, announced last week that it will give both hourly and salaried workers six weeks of paid parental leave. The policy, which will begin next year, extends to birth parents, adoptive parents, and foster parents.

Of course, companies in highly competitive fields got on the bandwagon even earlier, with Silicon Valley heavyweights like Facebook and Netflix making headlines for generous leave policies that act as recruitment and retention tools. A couple of states, including California and New Jersey, are also pushing companies to do the right thing by mandating paid leave, although any kind of federal solution to the issue seems elusive.

A lack of standardization also makes it harder for people who may be considering starting a family to determine if a potential employer's parental leave offering will work for them. For instance, some companies give workers flexibility as to when they take their leave after the birth of their child, so parents could stagger their time off. Some let employees break their parental leave up into smaller blocks, while others mandate that it be taken all at once. And some come companies might not pay workers their full salary during parental leave even if the time off is technically "paid" leave.

“More commonly, we’re seeing 60% income replacement for parental leave,” Brenna Shebel, director of healthcare costs and delivery for the National Business Group on Health, told Money.