It happens every spring. As part of your management program, take a few minutes to do an EXIT INTERVIEW to find out why the employee is leaving.
Some questions to ask: Were you able to do the job with the resources given? Were you properly trained? Did you have the right training coming into the job? What did and didn't you like about the work environment? Were you properly supervised? Do you have suggestions for improving the company or the product?
Take time to be an attentive listener. Don't turn the exit interview into a gripe session. Thank them for their time.