Millennials are now the largest generation in the American workforce, according to data from the Pew Research Center and from the US Census Bureau. They’re also the least engaged members of the workforce, and the most likely to leave your company.

Of course, employees of all generations leave companies all the time, and disengagement affects different workers for different reasons: they may not get along with their manager, find day-to-day activities unchallenging, or believe no career development opportunities are available to them. While a decent paycheck and benefits may be sufficient to keep some employees around, others will jump ship as soon as a better opportunity comes along — and this is truer of no demographic than millennials.

According to Gallup, 60 percent of millennials (born between 1980 and 1996) claim to be open to new job opportunities. Generational differences aside, the average American worker spends less than five years in every job, and a whopping 70 percent report feeling detached and uninspired.

So What Makes Workers Stay?

Hiring top talent is hard enough, but companies also need to understand what makes employees stay: a reputation as a revolving door is expensive and bad for business. Here are four things to keep in mind that keep workers around.

1. Professional development, not token freebies.

Perks are great, and if your company has the capital to offer them, your employees are likely to be happier. But espresso machines, in-office massages, and yoga passes won’t convince workers to stay — especially millennials. Young employees know the market is competitive and take every opportunity to focus on career development; immediate self-satisfaction, while nice, is no substitute for professional opportunities.

Today’s well-educated workforce has loftier goals, and career development is at the top of the list. Employees are more likely to stay with a company that offers training, education, and practical opportunities that will advance their professional interests. But don’t take our word for it: according to a recent study by Mercer, over 75 percent of workers surveyed indicated they would remain with their employer longer if they saw the potential for long-term career growth.

2. Mentors, not bosses. 

Traditional manager-employee relationships simply aren’t desirable for millennials. Following orders — especially from a boss who may be older, out-of-touch, and less technologically savvy — isn’t a productive paradigm for them, which means managers at older companies may need to adapt to keep their top performers satisfied.

On the other hand, there’s huge potential and demand for in-house role models, coaches, and mentors who have invaluable experience and institutional knowledge to impart. Millennials aren’t disrespectful or naïve, and they recognize the value of professional mentorship; as a result, they’re likelier to appreciate managers who take time to get to know them and who are willing to help them advance.

This shift affects workplace rituals, too: instead of annual performance reviews, have regular conversations and offer continuous, constructive feedback. Most of all, open communication rather than tired formalities will go a long way with millennial employees.

3. Exploiting strengths, not fixing flaws.

The wisest managers know that it’s better to leverage the talents of their employees than to correct their weaknesses. No employee wants to hear they’re bad at their job or need to change their strengths, interests, or passions to fit a role, and if they feel they’re expected to, they’ll leave. Instead, keep criticism short, sweet, and constructive, and assign responsibilities based on the capabilities and preferences of your employees.

Gallup suggests that a strength-based corporate culture is more likely to attract and keep stars. Because millennials aren’t satisfied with mediocrity, they want to feel they’ve been given the chance to make a difference at their company, performing well rather than just performing.

4. Flexible schedules, not 9-to-5 grinds. 

Here’s one that a little more concrete: millennials (and, increasingly, employees of all generations) enjoy flexible schedules. Thanks to digital technology, everyone is connected 24 hours a day, 7 days a week. If you expect your employees to be reachable outside of “normal” hours — and you should, since your customers and clients probably do — you need to give them additional flexibility in terms of when they’re expected to be in the office.

Policies that allow employees to work remotely and offices that open early and close late will be popular with your staff, encouraging them to work when there’s work to be done — and they’re likely to stay with your company longer. You may even save money! Plus, with telecommuting tools like Skype, Google Chat, and Slack, there are no longer many excuses to deny your workers flexibility when it comes to their schedules.

Key Takeaways:

Providing career development opportunities for employees while imparting institutional knowledge through coaches and mentors is a win-win strategy that will keep top performers around longer, especially if they feel their contributions are valued and specialized. Add in flexible schedules and remote work options and you’ve got a great retention plan that’s proven to work.