Is this in the U.S.? If I were a school administrator and half my graduating students were moving back in with their parents after graduation, I would consider my school to be failing terribly. I would expect even a community college to be better than that.

Alternatively, by "top private" do you mean very expensive, so most of the students were independently wealthy and were getting degrees in things not intended/needed to provide jobs after graduation? I just can't fathom going to / sending my child to a school where that was normal.

Yes, this is in the U.S.

"Top private" as in #1 in the U.S. News & World Report rankings. It's academically selective (slightly under 20% acceptance rate), and yes, very pricey for those not on financial aid. The demographics did skew toward children of upper-middle-class parents who wanted degrees in useless subjects. Liberal arts, after all.

BTW, this is not saying that 50% of graduates could not find jobs. There were a couple in that situation (mostly English, history, and language majors), but most people living back with their parents had jobs - in some cases, very good ones. I worked at a financial software startup. I had a classmate at the State Dept. Another friend was doing strategic analysis at MITRE (MIT Research and Engineering). All of us chose to live with our parents, even though we were making more than the median household incomes for our respective areas. Then there are more conventional live-with-parents stories, like the schoolteachers and librarians and baristas and unemployed.

It's more that if a large enough critical mass (say, all the English majors) chooses to live with their parents, it then becomes socially acceptable. And then their friends do it (while banking the rest of their salary), partially so as not to feel "different" from their less-successful classmates and partially just because they can.