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It can be difficult to predict the popularity of topics. Supervision may become a mainstay subject since new supervisors are always in the pipeline and even the senior ones need refreshers. I've had people in class who last attended a workshop on supervision around 30 years ago. Many, of course, were never formally trained. One day they were told, "Congratulations! You're a supervisor."
That's why it is not rare to hear a senior supervisor exclaim, "I wish I'd had this class when I started in this job."
— Booster Shot