Study details

For the study, researchers at Boston College tracked 2,896 employees across 141 organizations in the United States, Australia, Canada, Ireland, New Zealand, and the United Kingdom over a six-month period. Each company was given roughly eight weeks to restructure its workflow to maintain productivity before opting into the trial of a four-day workweek.

Two weeks before the start of the trial, each employee was asked a series of questions to evaluate their well-being, including, "Does your work frustrate you?" and "How would you rate your mental health?" The employees were asked the same questions after the six-month trial period. Researchers also analyzed changes in burnout, fatigue, sleep quality, and work performance.

Employees at the companies that switched to a four-day workweek were compared to those at 12 other companies that maintained the traditional five-day model.

The researchers found that workers whose days were reduced by eight hours or more reported the most significant improvements, which included reduced mental strain and improved physical health. Smaller reductions to hours also saw positive effects.

In addition, workers in the four-day trial group reported higher levels of physical and mental well-being than those in the five-day group.

The researchers noted that better sleep, improved effectiveness on the job, and lower levels of fatigue appeared to explain the improvements that occurred among employees who worked a four-day week.

"Increases in perceived work ability — at both company and individual levels — indicate that the work reorganization process opened up by four-day weeks has led to profound changes in the job experience itself, improving workers' individual and collective sense of performing their jobs well," they wrote.

"When people are more well rested, they make fewer mistakes and work more intensely," said Pedro Gomes, an economist at Birkbeck University of London. However, Gomes noted he'd like to see more analysis of the impact on productivity.

"When workers want to deliver the same productivity, they might work very rapidly to get the job done, and their well-being might actually worsen," said Wen Fan, lead author on the study and a sociologist at Boston College. "But that's not what we found." Rather, employees' stress levels dropped.

Fan also noted that more than 90% of the companies in the study decided to keep their four-day workweek after the trial, suggesting they weren't concerned about a drop in profits.

Overall, the study's findings suggest that "an organization-wide reduction in hours can stimulate workers to collectively adjust and optimize their workflows, leading to improved work ability and well-being," the researchers wrote.