In your opinion is there a clear career progression for chefs?
Yes and No. People interested in the culinary arts who are in the industry are doing just that.
When one enters the industry, they start out on the lowest rung and work their way up.
Chefs are managers and boss's already so, I fail to understand where you are going with this. Chef's always are trying to progess.
What level is the most common for chef to leave the industry?
Again.....as a Chef...