There are three occupations that have the lowest rates.....

The first would be Clergy. This would include Nuns.

By a more defined occupation I would say the lowest rate would be found among Popes. Not a single incident throughout recorded human history.

President of the United States is also an occupation that seems devoid of this, but there is some speculation that Harding actually died from it.

I am temped to say oil industry workers because over a many, many year period of working in a company that had around 80,000 employees I can only think of two cases. We actually discussed this once and decided that everyone was too tired at the end of the day to put forth the effort.