Studying Optimum Number of Students for Discussions

One of the biggest complaints from students who experienced virtual learning in the spring was that the student zoom ration was too high. While a lecture can have thousands of listeners, a seminar, language course, or discussion session can only have a small number of speakers. It is now grossly apparent that virtual classes quickly become painful and futile if just a tiny minority has any meaningful participation. Has the University conducted any studies on what the optimum number should be?