Women are just as likely to put away some money for retirement as men — but they are still way behind their male counterparts in total retirement savings, a new study shows.

Men had an average of $139,467 in their individual retirement accounts as of 2012, compared with the average of $81,700 that women had stashed in their IRAs, according to a report released Wednesday by the Employee Benefit Research Institute, a Washington-based research institute that focuses on health, savings and retirement issues.

As the chart below shows, women moved money to their IRAs just as often as men did. This was true for IRAs overall, which saw contributions for 10.9 percent of accounts held by women and 10.8 percent of accounts held by men; for Roth IRAs, which require people to contribute with after-tax dollars; and for traditional IRAs, which can include tax-deductible contributions.

So women with IRAs are just as likely to add to the accounts as men. But women, however, tend to make smaller contributions on average than men. In 2012, female IRA account holders contributed an average $3,995, compared with the average contribution of $4,023 made by men, according to the institute. The difference is slight, but that pattern held true for most age groups, according to the study.

A couple of factors could explain those smaller contribution amounts, says Craig Copeland, senior research associate with the Employee Benefit Research Institute. Some married women may be making joint IRA contributions with their spouses, and those accounts may be under their husband's name, he says.

But the most likely factor keeping women from saving as robustly as men is probably not that surprising: Women still make less, on average, when compared with men. Women earned roughly 77 cents for every dollar earned by men in 2012, according to the latest data from the Census Bureau. That was unchanged from the year before and not much higher than the 61 cents women made for every dollar earned by men in 1960.

That said, the wage gap is still smaller than the nearly 40 percent gap in total retirement savings balances seen between men and women, hinting that there must be something else at play. Some women may be limited in how much they can put away for retirement because of other financial responsibilities. Maybe they are single mothers delaying retirement savings to cover more immediate bills related to child care. Some women may think it's more important to set aside money for a home.

Investing habits may also play a role in determining why women have smaller balances overall, but there isn't enough evidence on gender-based investing preferences in retirement accounts to show decisively that women are more conservative with their investment choices than men. In fact, Copeland says, some studies show that some women may be just as aggressive with their investments as men with similar means.

A look at asset allocations in IRAs in 2011 showed that men and women had nearly identical allocations in bonds, stocks and cash. However, women had more money allocated to balanced funds, which invest in both stocks and bonds, while men were more likely to invest in other asset classes.

What makes the savings gap especially troublesome is that women generally need more savings than men to cover health-care expenses because they tend to live longer than men do.

That longer life expectancy could partly explain a shift that happens later in life, says Copeland. In 2012, men made bigger average contributions to IRAs for all age groups except for savers older than 70, when the average contribution of $4,644 made by women topped the average contribution of $4,632 made by men. That change could be a sign that women are more able to work and contribute to their retirement accounts in old age than men are, Copeland says.

Still, he is optimistic that women can catch up. "I would think, as women continue to become a larger percentage of the labor force and have higher incomes, that you would expect that this gender difference would go away," Copeland says.