Nearly all firms involved in one of the "world's largest" trials of a four-day working week will continue offering workers shorter hours.
Campaigners hailed the "breakthrough moment" for the radical policy with findings due to be presented to MPs on Tuesday.
The landmark results from the six month scheme involving 61 companies, found that 56 - or 92% - had decided to continue with a four-day week.
Among those 18 confirmed the policy would be a permanent change.
Involving over 2,900 workers, the study claimed that stress among employees reduced significantly, with a huge 71% reporting lower levels of burnout.
There was a substantial decline - 57% - in the likelihood an employee would quit.
Companies' revenue stayed broadly the same, the report said, with some seeing a rise of 1.4% on average.
The study - led by the think-tank Autonomy and research teams from Boston College and the University of Cambridge - also found a reduction in sick days.
Firms involved in the trial included a chippy in Norfolk, a consultancy company in Lancaster, and a construction business in Northamptonshire.
While there was no "one-size-fits all" approach, those who took part in the trial were able to join as long as they "maintained pay at 100% and gave employees a 'meaningful' reduction in work time".
Joe Ryle, the director of the 4 Day Week Campaign, said: "This is a major breakthrough moment for the movement towards a four-day working week.
"Across a wide variety of different sectors of the economy, these incredible results show that the four-day week with no loss of pay really works.
"Surely the time has now come to begin rolling it out across the country".
Research Associate at the University of Cambridge Dr David Frayne added: “The method of this pilot allowed our researchers to go beyond surveys and look in detail at how the companies were making things work on the ground.
"We feel really encouraged by the results, which showed the many ways companies were turning the four-day week from a dream into a realistic policy, with multiple benefits.
"We think there is a lot here that ought to motivate other companies and industries to give it a try".
