Both workers and companies like the idea of a four-day, 32-hour work week, a large pilot project in the United Kingdom has found, The Washington Post and others reported.

The results, reported after a six-month pilot project, the largest of its kind to date, found that that 56 of the 61 British companies that took part would continue four-day workweeks after the pilot ended; 18 of the 56 said that the schedule change would be permanent. Two companies are extending the trial, while only three would not continue it at all.

The shortened work week was so popular with the nearly 3,000 employees who took part that 15 percent of them said that “no amount of money” would entice them to go back to a five-day week. Nearly a third said that they would require a 26- to 50-percent pay increase to return to five days a week, and 8 percent said they would want a pay hike of 50 percent.

The pilot was organized by advocacy group 4 Day Week Global in collaboration with the research group Autonomy, and researchers at Boston College and the University of Cambridge.

Among the findings were that employees reported a range of benefits related to their sleep, stress levels, personal lives and mental health, while resignations decreased. Companies reported “broadly the same revenue” during the course of trial, but their revenues rose by 35 percent on average when compared with a similar period from previous years.

An earlier, smaller pilot, also organized by 4 Day Week Global, involving many countries, resulted in increased revenue, reduced absenteeism and resignations and improved employee well-being, the Post reported. None of the 30 participating companies, comprising 1,000 workers, planned to return to a five-day workweek.

That pilot also found that revenue rose an average of 38 percent when compared with same period in previous year, and that 70 percent said that they would need a 10 percent to 50 percent pay increase to return to a 40-hour work week.

The Post noted that the most of the companies that took part in the most recent U.K. trial were small; about two thirds had 25 or fewer employees.

Participants in the survey preferred the 32-hour week for reasons such as a better work-life balance and child care.

Opponents of a four-day workweek claim that is infeasible for those in certain industries, that some would rather work more and earn more, and that it would hurt productivity, the Post reported. Proponents say that societal benefits include lower health-care costs and reduced emissions from daily commutes.

The five-day, 40-work week was first proposed in August 1866, according to the Library of Congress, and it was established by the Fair Labor Standards Act of 1938, according to the U.S. Department of Labor.

“A hundred years ago, we moved from working six day weeks to five, and we’re overdue for an update,” 4 Day Week Global stated on its website.