Married, I would say probably a 25-35% depending on schools (I think its more common for internationals these days). I would say another 15-20% start with serious relationships and about the same finish...some existing couples break up and some new ones form during the two years.
No matter what your situation, you will find people in similar ones. I had friends in just about any relationship/non-relationship scenario you can think of. Married w/ and w/out kids, divorced, married living in different countries, married and both in school (same and different schools), engaged, dating and living together, dating and not living together, single and looking for something serious or chasing undergrads...gay, straight...Its a slice of our demographics. I had friends who had a new relationship every week and some who had 5 kids and a minivan.
Kellogg Class of 2010...still active and willing to help. However, I do not do profile reviews, don't offer predictions on chances and am far to busy to review essays, so save the energy of writing me a PM seeking help for these. If I don't respond to a PM that is not one of the previously mentioned trash can destined messages, please don't take it personally I get so many messages I have a hard to responding to most. The more interesting, compelling, or humorous you message the more likely I am to respond.