That's an increase from 15.6 percent reported from the previous Rosenberg Management of an Accounting Practice, or MAP, survey.
The biggest firms in the survey had a larger percentage of female partners– in the high teens or low 20s, percentage-wise, Rosenberg said. And even smaller, local CPA firms have been boosting their percentage of women partners from around 13 percent five years ago.

Nevertheless, retaining talented female staff and developing them into partners remains an important issue within the accounting industry, Rosenberg said.

The 2014 Accounting MOVE Project has reported that women essentially evaporate from accounting firms' partnership pipelines; they comprise 51 percent of employees at accounting firms but only 19 percent of partners and principals.

Many women in accounting disengage from earlier plans to become partner when they have hazy ideas of not just what it takes to become partner, but also what is involved with being a partner, Rosenberg said. Lacking clarity and facing life choices about family and balancing work, they may become convinced becoming partner is unattainable.

"They develop this mindset that it's not possible to be a partner and be a female in this firm," Rosenberg said. "You've got to show them at an early stage that you don't want them to de-select from the female partner career path."

One way to do that might not feel particularly comfortable to many men who are partners at the firm, he said, but it can go a long way toward showing women that the firm values them and welcomes their efforts to make partner. He suggested that partners talk with female staff who have been with the firm four or five years about how much they are valued, recognizing that many women in their late 20s may get married and begin to have children.

"It's almost like having the birds and the bees talk," Rosenberg said. "You sit down and say, 'If you get to the point where you're thinking about raising a family, I want to let you know that there's nothing we won't do to help you.'"

"Firms need to be proactive," he said.

Another important way to retain staff, especially women, is to provide mentors who can discuss what it takes to become partner and provide feedback periodically on specific ways tackle such requirements as developing new business. Mentors can also provide help with networking and ensure the top talent isn't getting so bored that they look at competing firms or leave for work as a management accountant.

"You want them to have someone safe that they can talk with," he said. "A firm has to find ways to keep it vital, to keep it interesting, and that's where mentoring comes in."