People's memories differ, and I'm not sure where to find box scores from that era to confirm actual attendance, but I remember nice crowds (well into the 40s) for most Big Ten home games during the Mallory era, and some games where the place was packed. I was at the 1987 game against Michigan, where Schembechler complained that our crowd was too loud. We were 5-1 going into that game (and had beaten Ohio State earlier that season - - "the darkest day" for Earle Bruce - - but it turned out that OSU wasn't very good that year), the game was played in a steady rain, and there wasn't an empty seat in MS.
Fast forward to 2007 - - the Bucket game. Yes, there was some added emotion that season (Coach Hep's passing and the "play 13" mantra) but, at just 6-5, we filled the place and it was the one of the most electric sporting event atmospheres I've ever experienced. And forget about people leaving in the second half. No one left early. I have pics of the on-field celebration after the game ended and the stands were still full.
Here's my spin. Obviously this is just conjecture, but I get the sense that there are a lot of people who are champing at the bit for a winning football team and will support the team in person if we win more consistently. I think we'd routinely see attendance in the mid to high 40s, and 1-2 sellouts a year. I don't know that we'll ever see a sellout for an OOC game, but even some of the big boys have plenty of empty seats for the non-conference schedule.