Anyone trying to hire tech talent these days knows we're in the midst of a legendary seller's market, with lavish workplaces, free food, and unlimited time off becoming "table stakes" if you want to hire skilled software engineers. 

In this tight labor market, it's surprising that many tech companies don't seem to mind driving a lot of their tech talent out the door. But as new research shows, that's exactly what's happening.

The recruiting firm Battalia Winston recently surveyed 160 women engineers across a wide variety of industries to find out why they leave their jobs -- and why they stay. Forty-four percent of respondents said they'd left an employer in the past five years, and of those, 55 percent said they left because of a company culture that was unwelcoming to female engineers. 

Some of them got specific. One complained her workplace had a "strong 'brogrammer' culture." Another noted: "It was a very hierarchical company that seemed to exclude women from an all-boys club." A third described a "toxic environment" that, she said, only favored "a small clique of white men."

None of this is news. Earlier this year, a scathing report by some female Silicon Valley insiders detailed just how awful things really are. But you have to wonder if the (mostly male) tech company executives, CTOs, and hiring managers out there truly don't mind losing skilled engineers because of a company culture stuck in the Stone Age. It's worth noting that all the respondents in the survey were working as engineers when they provided their responses which means some other company had snapped up the talent their previous employers failed to value enough.

What do employers need to do to keep female engineers in their roles? The study's authors offer some no-brainer suggestions that every company everywhere should follow. If you're not already doing these things, it's more than time to start.

1. Create zero tolerance for workplace sexism.

This should, of course, apply to all employees and not just those in engineering or STEM roles. Training to help employees avoid both conscious and unconscious gender bias is a start. So is a clear procedure for reporting and dealing with gender discrimination and sexual harassment. 

But those measures in themselves aren't necessarily enough, as most women in tech who've filed complaints wind up unhappy with the results, and often end up leaving their companies. The message needs to come from the top that gender bias and sexual harassment will have a negative effect on the perpetrator's compensation and advancement. So will the inability to retain employees of either gender.

2. Offer a clear path to advancement.

Every employer should do this for every employee, even if the path to advancement will eventually lead the employee out of your company. But at many companies, it isn't being done for women in engineering roles. Of the women who had left engineering jobs, a third said they did so at least in part because there was no clear path to advancement for them. "I was not being mentored or given appropriate responsibilities, or the opportunity for growth," one respondent said.

3. Create specific policies to promote work-life balance.

Of the women engineers who'd chosen to stay with their employers, 78 percent said work-life balance was one big reason why, making it their top concern. As the report's authors note, "Organizations must do more than add work-life balance to their list of corporate values. A commitment to work-life balance must be translated into real-world policies: flexible schedules, support and accommodations for employees with children and aging parents, competitive maternity leave, benefits and sick leave, etc."

Employees who take advantage of policies such as these should be able to do so "guilt-free," they noted. Otherwise, the policies might as well not exist. This is smart for any company, whether you're trying to retain female engineers or not, because there is ample evidence that employees who can  take time off when they need to and have full lives outside of work are likely to be better at their jobs and also healthier.

And, yes, it is a powerful took for retaining female engineers. One respondent said it made a difference to her that she knew she could have a life outside work, and that she'd seen women at her company win promotions even after they'd gone on maternity leave, reduced hours while performing child care, and then returned to work full-time. 

"I've seen these things at my company," she reported. "And the respect for my company keeps me when others come calling."