In discussions about efficiency, different conceptions of the nature of education become significant. If education is about transferring pieces of knowledge from a learned person to a student, then the difference between a 400 student lecture course, a 30 person classrooms, a 15 student seminar, or an unlimited enrollment in an online course may be limited (although more personal interaction, in my experience, can enhance the acquisition of knowledge). However, if education is about more than becoming a walking encyclopedia, then the interaction with and feedback from a professor can be much more effective in developing skills and exploring, as briefly discussed in the previous post. The small group dynamics of a seminar, along with individual attention and advising, can be vitally important, perhaps even more efficient, for encouraging a student to explore and training him/her to approach topics in news ways and to think creatively and critically. Those skills become much more difficult to develop with large enrollments and online courses.
The less popular, presumably less marketable majors result in particularly inefficient departments, if enrollment numbers are the only benchmark. However, in these small departments, students often find greater space to explore, more individual attention, and extra opportunities to develop important skills. When we consider the variety of learning styles and backgrounds of our students, small departments may be even more important for helping some students reach well beyond whatever they could have imagined.