What yardstick can we use for experience? Some employers introduce a Total Time element, but that is flawed by the long haul/shorthaul differentials in experience. It would be unwise to use training and sim records. Admitting to ones shortcomings in the bi-annual humiliation session in the sim is a very important part of air safety and could never be seen as 'competitive'. In most professions the bull!!!!/personality factor is an acceptable part of promotion, but not so in aviation.
So we are left with 'Company Time' as the most practical form of seniority. There are often training posts available for sideways promotion of experienced guys who are new to a company.