BLUF. Am I being too "nit picky" about metrics for people's annual goals? 

More specifically, let me give a case example. I want to set a goal for each of my managers to hold a 1o1 with each of their directs once a week. The metric could be something like "average weekly completion rate". They'd need to log data to get their completion rate for each week and then average those numbers at the end of the year. 

My question is this. Do I require them to keep all this data in a some shared worksheet so everybody can see everybody else's data? Or do I let them just report their numbers based on data they keep themselves? I don't wish to seem distrustful or OCD. And, I don't want to enable anyone to "game" the system.