Typically eloquent piece by Simon Caulkin in yesterday's Observer: The devil is in the details:

How would you appraise a vicar's performance? By the number, length and quality of sermons? Attendance at church? Out of wedlock births? Ratio of marriages to divorce? Doctrinal purity?
This intriguing question was raised by proposals put forward last week by the Church of England's General Synod to make incompetent vicars easier to sack, and to subject them to the kind of performance measures that apply to other workers.

Don't laugh:... In one study, a Norwegian hospital chaplain had performance measures that counted not only bedside visits, but also the number of last rites he performed. In fact, the church's measurement problem illustrates with blinding clarity the tensions inherent in all performance management.

Caulkin does a great job articulating the paradox of performance measurement. If you are in too much rush to read the whole thing, here's his key point:

If performance management is both inevitable and impossible, what's to be done? The answer is to disconnect measurement from control - to reconceptualise it, as professor Andy Neely of the Advanced Institute for Management Research has put it, as a system of learning rather than control.

Yes... mind you, that's how schoolteachers tried to "sell" me on exams; they had a hard time convincing me of their sincerity!