And what is the correlation between happiness and 'productiveness', or more to the point, profit? Ibankers and junior associates at white shoe firms are overwhelmingly miserable, and still a) people line up for their jobs; and b) they make their firms a multiple of most other jobs (maybe with software being an exception, but let's not delude ourselves into thinking that tech companies are successful just because they have great engineers).
Correlation isn't causation in either direction in this case. Among the many reasons for long hours for finance, productivity and profit are quite low on the list. "Face time" is a phrase for a reason.
