London (CNN Business) — The verdict is: a four day work week it’s good for business.

After six months, most of the 33 companies and 903 workers who have tested the schedule, with no pay cuts, are unlikely to return to the standard work week, according to organizers of a global pilot program.

None of the 27 participating companies that responded to a survey conducted by 4 Day Week Global said they were leaning on or planning to return to their old five-day routine. About 97% of the 495 employees who answered said they wanted to stick with a four day week.

Most of the companies participating in the test are based in the United States and Ireland. Survey respondents rated their overall experience 9 out of 10, based on productivity and performance.

The workers were just as positive with the trial, reporting lower levels of stress, fatigue, insomnia and tiredness, as well as improved physical and mental health.

The trial is also good for the company’s profits. Average income increased 38% over the same period last year, according to the survey.

4 Day Week Global, a non-profit organization, collaborated with researchers from Boston College, University College Dublin and the University of Cambridge for the exam. It was divided into two groups, starting in February and April this year.

Juliet Schor, a professor of sociology at Boston College and the trial’s principal investigator, said employees did not report an increase in the intensity of their work.

This shows that the work reorganization strategy was successful and performance was not achieved. [acelerando]unsustainable and undesirable”, he said.

Win win

Jon Leland, chief strategy officer at Kickstarter, a crowdfunding site that participated in the test, described the timeline as a “true win-win.”

“The four day week has changed our business and our people. Staff are more focused, more engaged and more dedicated, helping us achieve our goals better than ever,” he said in a statement.

A separate six-month trial in the UK, also run by 4 Day Week Global, and involving 70 companies and 3,300 workers, finished this month. The trial results—the the biggest in the world to date—to be published in February.

Earlier this year, workers in the UK carried out a trial run explained to CNN Business how the extra day off has improved their lives, giving them more time to run errands, pursue hobbies, and simply recharge.

Calls to shorten the work week has gained strength in recent years. As millions of employees have shifted to remote work during the pandemic—reducing travel time and costs—the phone has only gotten louder.