A University of Chicago study, “Job Satisfaction in the United States,” reports that clergy are the happiest on the job, with 67.2% of respondents describing themselves as "very happy".
The next highest job satisfaction is fire fighters, at 57.2%.
Happiness is a worldly thing which can be lost. Because God is the source of the supernatural grace which we call joy, those who love and serve him share in that grace, which abides even in the presence of worldly sorrow. Will they do a study that measures "joy" on the job?