[phpisthebest]

>Employers don't know ahead of time which employees will leave and which will stay

I may be a bad example, but I can assure you every employer I have ever left new I was unhappy in my role before I left.

I always have frank and open conversations with my managers about my expectations for growth, wages, etc. These are not Ultimatums, but more "In 5 years I would like to be" type conversations.

Now as a manager I have gotten similar feedback from people that work from me, sometimes you have to listen closely to understand what they are saying in reality as many are not as direct as I am, but the feedback is there

I think managers just simply ignore it in most cases