A recent article in a financial journal explained that companies which implemented a four-day workweek reported a significant increase in overall employee morale and a 15% increase in productivity compared to their five-day workweek counterparts. However, the article also pointed out that these companies had completed other initiatives targeting workplace engagement prior to instituting the shorter workweek, including mandatory team-building exercises and enhanced flexibility in work schedules.
Which of the following pieces of information, if true, would most help to strengthen the argument that the four-day workweek itself is the primary reason for increased employee morale and productivity?