Indeed. I think the most cost, effective, and resource-efficient pedagogical method for undergrad would be {best video} + {played in a lecture all} + {with a TA

Indeed. I think the most cost, effective, and resource-efficient pedagogical method for undergrad would be {best video} + {played in a lecture all} + {with a TA breaking the video into chunks and asking for questions} + {TA session with smaller groups}. Redoing 90% of the same lecture yearly, by faculty whose time could better be spent researching, is insane. But any change in teaching upsets a lot of academia economics, which are tenuous as-is. I expect it'd take a federal mandate to make the above shift (a la ACA and electronic health records).