Yeah i think overall happiness is logical, but personally I would be interested if there is a link between worker's control and quality of life indicators like longevity, vacation days, job security, hell even something like hectars of parks or commute time.
But, I suspect, there will be no real clear trend because workers control both diffuse and closely intertwined with other processes, like nominal worker's control (e.g., companies whose shares are owned by employees or small businesses) versus what we on the left think of as worker-controlled, such as a coop.
Nevertheless, you might want to look at different industrial regions in modern Japan, in particular companies that are still dominated by factories practicing "jiko-kanri" and factories where there is a rigid hierarchy like in the west might have surprising differences in, for example, measures like job satisfaction.
百花齐放
-----------------------------
la luz
de un Rojo Amanecer
anuncia ya
la vida que vendrá.
-Quilapayun