Ask the groups to survey their members about issues and strengths. Being generous to spouses, friends and children puts more people on the team trying to get them to stay. Reward managers and teams for retention - Managers seldom do things that are not measured. So reward managers for keeping high performers and key talent. Identify them and develop job tasks and motivators to keep them on the job.
Exit interviews are poor ways of finding out why people quit.
The fear of retribution and the desire for good references often skews the answers. This helps to identify new issues and trouble spots. Hold focus groups to identify general things that frustrate them. Post exit surveys - Months after a separation do a sample survey and ask them why they left and compare to you exit data. Expect significantly different answers.