Well the effect says it scales, however, everyone on reddit says that it doesnt and its a flat 50% as long as you are 1 level lower than your max job. Which is why my first post probably didn't get rated up, but worthless posts after it with no new information/incorrect information got excellent ;-p, because most arent aware that it is just 50%.
Just a response to this, it may currently be that it is a Flat 50% bonus in testing/actuality. However, even the in-game help says that it scales based on the level difference. It may be a bug, it may have changed after the in-game text was added and that never updated.
I personally haven't tested the bonus thoroughly myself and going off the assumption of what SE has said.