We expect that kind of attrition in all places of higher education. Any executive who is complacent with losing one of every two customers should be replaced. An exit interview. Only a sample. Invite them into your office, perhaps for lunch and explore the reasons why they did not return.
Nothing is more flattering than a personal invitation to the president's office.
You will be amazed with what you learn. Of course there are many reasons. Some are economic necessity, but others are more subtle. Researchers wanted to discover what factors explain the success of the 3 people in 10 who make it. Education, age or socio-economic status had nothing to do with it.