Less than one-fifth of newly-appointed CEOs at US companies in 2017 were women.

That’s the finding of new research from outplacement consultancy Challenger, Gray & Christmas, released this week. The firm’s research looked at how many women were hired to replace outgoing CEOs last year, across nearly 1,000 companies of different sizes.

Of the 993 newly hired CEOs that Challenger tracked, just 183, or 18.4%, were women. That’s about the same as last year, when 18.5% of all new CEO spots were held by women.

“The tremendous strides for women in the workplace following the #MeToo and #TimesUp movements have yet to be truly felt in the C-suite,” said Andrew Challenger, the firm’s vice president, in a statement.

According to Challenger’s tracking, some industries have a better track record of hiring female CEOs than others. The most promising were the government/nonprofit sector (58 new female CEOs were appointed in 2017, or 42.3% of all the incoming CEOs in that industry), followed by the financial sector (24 new women CEOs this year, or 21.6%), and hospitals (22 new women CEOs, or 25.6%). At the opposite end of the spectrum, the commodities, automotive, chemical, and telecommunications industries saw no CEO roles go to women in 2017. And the aerospace/defense, energy, and transportation sectors gained just one new female CEO each.

“A lot of those industries are very technical in nature and they require STEM degrees… and there’s a lot of research that shows that, at least in the American education system, women tend to be systematically shunted to other fields in comparison to other countries,” said Columbia Business School professor Rita McGrath. “For example, in Iceland and Finland, there’s no difference between men and women,” in the number of men and women who have STEM degrees. That means that in the US, “there’s less of a pipeline,” of female STEM talent to draw upon, says McGrath.

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But the issue is deeper than that. “There’s no precedent [of female leadership] in these companies — aerospace, military, some of the cutthroat investment banking environments,” and that creates a self-perpetuating cycle that holds women back, says Anna Tavis, clinical professor of human capital management at the New York University School of Professional Studies.

Tavis believes the answer is in boosting the number of women in any organization to above 30%, pointing to oft-cited research from the 2016 book “What Works: Gender Equality by Design.” According to Challenger’s data, the two industries where this was the case in 2017 — government/nonprofit and education — both saw women comprising more than one-third of their incoming CEO cohorts.

Though so many industries saw so few women take over leadership positions, 2017 did see some modest gains for women. For instance, the number of female CEOs on the Fortune 500 list increased from 21 in 2016, up to 32 in 2017 (growth of 50%). And Geisha Williams, the new CEO of PG&E who took over in March, became the list’s first Latina CEO.

McGrath concluded that it would be in many companies’ best interests to bring on, and promote, more women. “More diverse and inclusive workplaces systemically do better.”