According to a survey of participants published on Wednesday, the majority of companies participating in a four-day workweek pilot program in the United Kingdom reported no loss of productivity during the experiment, and in some cases reported a significant improvement.

Nearly halfway through the six-month trial, in which employees at 73 companies receive a paid day off weekly, 35 of the 41 companies that responded to a survey said they were “likely” or “extremely likely” to continue the four-day workweek after the trial ends in late November. Except for two of the 41 companies, productivity remained constant or improved. Surprisingly, six businesses reported that productivity had increased significantly.

The idea of a four-day workweek has been discussed for decades. Former Vice President Richard M. Nixon predicted it in the “not too distant future” in 1956, but it has yet to materialize on a large scale. However, changes in the workplace caused by the coronavirus pandemic, such as remote and hybrid work, have given rise to concerns about other aspects of work. Is it just because we’ve done it for over a century that we work five days a week, or is it the best way?

Some trial company leaders stated that the four-day week gave employees more time to exercise, cook, spend time with their families, and pursue hobbies, improving their well-being and making them more energized and productive at work. Critics, on the other hand, are concerned about increased costs and decreased competitiveness, especially since many European firms are already trailing rivals in other regions.

According to Jack Kellam, a researcher at Autonomy, a think tank that is one of the trial’s organizers, more than 3,300 workers in banks, marketing, health care, financial services, retail, hospitality, and other industries in Britain are taking part in the pilot, which is one of the largest studies to date.

It was too early to tell how the shortened workweek had affected productivity or the company’s bottom line at Allcap, one of the pilot companies, said Mark Roderick, managing director and co-owner of the 40-person engineering and industrial supplies company. Overall, employees were pleased with the extra day off, and the company was considering continuing it.

Mr. Roderick appreciated the new schedule because it gave him more time to train for a recent Ironman Triathlon in Wales. Even so, some days are more stressful than others, because summer vacation and the shorter workweek have stretched staff thin. “We’ve all been under the cosh a bit,” he admitted, using a British expression for “in a difficult situation.”

Experiments similar to the one carried out in the United Kingdom are also being carried out in other countries, primarily in the private sector, including the United States, Canada, Ireland, New Zealand, and Australia. In a trial in Gothenburg, Sweden, officials discovered that employees did the same amount of work, if not more.

The four-day workweek was such a success, according to Jo Burns-Russell, managing director of Amplitude Media, a marketing agency in Northampton, England, that the 12-person company hoped to make it permanent. Employees have discovered ways to work more efficiently, according to her. As a result, despite the fact that half of the employees are off on Wednesdays and half on Fridays, the company continues to grow.

“It’s definitely been good for me in terms of not constantly pinging from thing to thing to thing,” Ms. Burns-Russell said. She has taken up painting as a hobby and is feeling more at ease. August is typically a slower month for the firm, so the real test will be how the experiment plays out over the next few months as the company grows, she said.

Gary Conroy, the founder and CEO of 5 Squirrels, a skin care manufacturer based in Brighton, England, that is taking part in the trial, stated that employees had become more productive while making fewer mistakes, and that employees were collaborating better.