More than 3,300 workers in 70 companies across the United Kingdom are testing a four-day workweek to see if they can keep their productivity up. “We’ll be analyzing how employees respond to having an extra day off, in terms of stress and burnout, job and life satisfaction, health, sleep, energy use, travel and many other aspects of life,” Juliet Schor, a sociology professor at Boston College and the lead researcher on the project, said.