This comes from profession.rsc. It is in a section entitled "RandomSelection _deathSelector". It is my guess, from observation in the game, that "Years" is how often the dice are rolled for a death in that profession, and "Population" is "one in".
Profession Years Population
Stonecutter 1 30
Miner 4 30
Builder 5 100
Hunter 5 100
Forester 5 100
Gatherer 10 100
Fisherman 10 100
Woodcutter 10 100
Herbalist 10 100
Blacksmith 10 100
Farmer 25 100
Hersdman 25 100
Vendor 25 100
Trader 25 100
Physician 25 100
Laborer 50 100
Brewer 50 100
Tailor 50 100
Teacher 50 100
Cleric 50 100