I was able to get all 115 sets. How?
1. I phoned (leaving voicemail if necessary) to say the packet of questionnaires was coming, and passionately explained how much students would benefit from the book, which would be based on the questionnaire responses.
2. I immediately sent the packet.
3. The day after they received the packet, I called (again, leaving voicemail if necessary), asking if they'd mailed the completed questionnaires back. Again, I passionately explained the importance of doing so.
4. If I didn't get the packet back quickly, I called again the next day and, if necessary, the day after that.
I never had to make more than 3 follow-up calls--I got the completed packet from 115 of the 115 colleges.
So, in short, my approach to getting a high response rate:
Call (passionately), email, call, call, call.