Research, exit interviews, and our own experiences tell us over and over again that the number one reason employees leave a job is their direct manager.

But why? What are managers doing (or not doing) that prompts employees to look for a way out?

It’s poor communication skills. Specifically, they don’t listen.

Like everyone on the team, bosses have a range of technical, leadership, and interpersonal strengths. Employees don’t expect their boss to be perfect. They do, however, expect the boss to listen to them. Employees are willing to work with somebody who’s flawed or lack skills in any one of these areas, as long as they know they can have a conversation–and be heard.

The ability to engage, share feedback, and walk away feeling like their manager listened — even if they ultimately didn’t get what they wanted in the request — is essential. It’s so important, in fact, that employees who are ignored or dismissed repeatedly will leave at the first opportunity.

For a moment, think about a bad boss you’ve had — or have now (I’m sorry). What you are likely to recall are nasty emails, unrealistic demands, broken promises, and confusing or conflicting guidance. These behaviors are all made worse if their tone is sarcastic, demeaning, or loud.

However, the straw that broke the camel’s back, the experience that led you to leave, was likely a time you tried to speak up and weren’t heard. Employees will tolerate some bad boss behavior if they feel there is a chance they can influence or change that behavior in the future. As soon as they feel shut down and have no recourse — they’re not being listened to — employees see no other path out of the situation but to leave.

So, bosses who want to improve retention should first focus on their listening skills. Through this single improvement, they’ll start to hear other areas that can be addressed. However, without this first critical step, they simply won’t know where to start.

Improving listening skills requires you to do four things:

1. Create time and space to listen. If you’re too busy to meet with employees, no one will have the chance to speak up. Like a professor who has office hours, a manager could have an hour or two dedicated solely to listening to what employees have to say.

2. Be fully present. No multitasking. The exception would be walking and talking if that helps take some of the pressure off meeting face-to-face.

3. Commit to not responding or reacting at the moment. Make some interactions simply about hearing the other person without saying anything in response. This tactic helps you avoid coming off as defensive or rushing to a solution that may or may not work.

4. Repeat back what you’ve heard. Ensure you have understood your employee by repeating what he or she has said. This reflective strategy gives them a chance to confirm or make any corrections.

Know that no one is perfect in articulating their issues. Everyone needs an opportunity to be heard on multiple occasions as their own beliefs and interpretations evolve. Listening isn’t a one-and-done event. Allow employees to change their minds or clarify any misunderstandings.

For employees, sharing feedback, concerns, and recommendations with the boss is the only avenue to improve a bad situation. When that shuts down, they have no reason to stay. The good news is that managers can dramatically improve employee retention by enhancing their listening skills.