NCT Controller reported Supervisors only have to maintain operational currency on two positions; which Reporter believes compromises the operation.

Narrative

This is not a specific aircraft incident. Rather this report is to highlight a operational safety problem at the facility. The Air Traffic Manager requires operational supervisors to train/certify on only 2 sectors within the supervisor's designated area of operation. At other TRACON's operational supervisors are required to train and certify on all sectors to which the supervisor will oversee. Each area at NCT has on average 5 sectors; some have more. The consequences of this practice is having a negative impact on the facility regarding service and safety to the users. Operational incidents are occurring with more frequency and with increased severity. Some operational supervisors are unable to certify on their originally assigned sectors. For example; the San Francisco and Oakland finals; Oakland and San Francisco departure sectors. This results in management's decision to move the supervisor in training to a slow sector with little difficulty in order to receive certification. Supervisors are not held to the same training standard as controllers in training. (developmental) As a result; supervisors are overseeing an operation they themselves cannot work. This has consequences to the operation. The biggest impact is training. Individuals in training are assigned to specific supervisors. So basically; you have a supervisor who could not certify on certain sectors; overseeing training on the sectors they themselves cannot work. The policy at NCT allows supervisors to certify controllers on all sectors within their operational area. I think this policy speaks for itself. I can't imagine airlines allowing people who cannot pilot an airplane performing certification check rides on B747s. This isn't the only factor affecting the level of service; but it is an important place to start. Supervisors should have to certify to the same standards as controllers on all sectors and maintain more than 8 hours a month on position. San Francisco can run a 36 rate when in trail to Runway 28. At times it goes down to 25. Why? Skill level. That's a lot of gas wasted in holding and delay vectors.