Yes, we use formal job descriptions as part of employees’ performance evaluation but it is not the largest factor in determining whether someone receives a pay rise.
We use formal job descriptions (the baseline) more as a tool for firing employees who fail to meet the basic demands of the job. When we are looking to promote someone, this person MUST have proven their will and ability to rise above the basic requirements and do anything or everything in his power to do what is best for a task.
Someone who leaves at a fixed time everyday and does just what he needs to do will likely retain his job, but is highly unlikely to be considered for promotion.
the most recent example was amongst our 3 new interns; all of them were proficient in design which is why they were given places, but only 1 would constantly stay late producing more drafts than asked, and he would follow the entire project through to print and client delivery (he asked to be allowed to attend client meetings). the other 2 would just pack up and leave at 5.
it’s immediately clear who got promoted and who we will likely let go in the future.
* to be fair, we do tell all new employees that we pay attention to those who wish to excel and those who just want to make ends meet.