Back when I was in management, I used to collect concrete metrics like "you keep closing work items, but it's been three months since you checked in any code" o

Back when I was in management, I used to collect concrete metrics like "you keep closing work items, but it's been three months since you checked in any code" or "you're employed as a tester but you only opened two bugs last year and they were both by design". Of course people could game it, and maybe they did, but it went a long way toward identifying the people who were just straight-up asleep at their desks.