The excerpt doesn't come from a paper -- it comes from the book The Overworked American: The Unexpected Decline of Leisure, by Juliet B. Schor: http://groups.csail.mit.edu/mac/users/rauch/worktime/hours_w... If you want to be snarky, get the details right.

Peasants' work output were calorie-restricted. 11 hours backbreaking were the norm during harvest, but not in the less busier seasons. In the northern countries, snow and lack of sunlight made working impossible for several months per year. Instead, they ate very little food slept through most days.