CEP Ranking Process:

Step 1: lump all MXOs in the same division
Step 2: arrange MXOs in ascending order (No. 1 = highest CEP)
Step 3: End

Note that getting good performance grade is not the same as having high CEP. For example, a newly promoted MX11 who got promoted in 2011 will automatically gets a performance grade of "C" for 2012 but can still maintain a high CEP of MX9/10.

Age also plays a part. An officer who is about to retire is expected to reach his/her CEP. E.g. A MX11 officer age 58 is MX11 will only have a CEP of MX11.