CEP is arbitrary and is being looked at on an annual basis (i'd know because I've done ranking exercises for my staff). Your CEP will normally be at least 1-2 grades higher than your current CEP. If you enter fresh as an MX13, your CEP is going to be MX11. If it is more than 3 grades higher, then the reporting officer has to do a write-up on the officer to explain why he/she deserves a CEP that is 3x higher. Believe me, many bosses hate doing write-up unless you're truly exceptional. I had to do a lot of write-up when I gave one of my staff an "A" grade performance and a CEP that is 3x higher... in the end my staff got a "B" and 2x CEP grade.
When you get a promotion, your performance grade will be an automatic "C" (exception applies) for the following year... your CEP however, may be maintained/stopped/increased. So you can be an average "C" performer but maintain a high CEP. Age matters for CEP. If you're 50, an MX11 with CEP of MX10, you'll be ranked lower than an officer who is 30, an MX 11 with the same CEP. Anyway, ranking isn't exact science and there are too many factors to consider.
Be realistic when you're in a Ministry and not a scholar
