Let's take this for face value, the higher class an event is percieved, the less BM will show on top of that, if a men and woman aren't promoting an event together, it does affect the ratio of attendance. "Lower class" events with good promoting = better ratio of people.
But IMO, I think single mixer events attract a certain crowd of person, and it's actually better to show up events/activities around hobbies. That way you create a good connection around a thing or goal, and you also expand your network