The results come from a series of four-day-workweek trials conducted in the U.S., Canada, the U.K. and Ireland over the past 18 months. Dozens of companies ranging from design agencies to manufacturers and nonprofits tested the four-day concept, an approach that is gaining traction as employers and employees rethink the traditional ways of work. Workers were given a paid day off a week but the same workload to see whether they could get as much done working more effectively.

After six months, workers said they had less burnout, improved health and more job satisfaction, and had cut their average work time by about four hours to 34 hours a week. Those who continued the schedule a full 12 months reduced working times even further, to about 33 hours a week, researchers say. Meanwhile, they continued to report better mental and physical health and work-life balance.

The idea of working less than the conventional 40 hours over five days a week has been kicked around for years but has found new momentum recently. Some employers and policy makers are exploring whether a four-day week can improve employee well-being and loyalty and help them compete for workers.

Up to now, most studies of four-day weeks examined the short-term effects. The new findings are the first that look across multiple companies over a longer, 12-month period. They suggest that businesses and employees both benefit in the long run as workers get accustomed to shorter weeks, companies and researchers say.

Most companies didn’t ask workers to“speed up and cram five days of tasks into four,” said Juliet Schor, an economist and sociologist at Boston College whose team helped conduct the study with the nonprofit advocacy group 4 Day Week Global. Instead, they reduced meetings and dedicated more time to uninterrupted focus work, she said.

Companies in the U.S. and Canada recently concluded a smaller pilot of a four-day week led by the same researchers, and similar trials are in the works in Australia, Brazil and elsewhere. In a U.K. trial involving 61 British companies last year, the majority of the participants said they would stick with the four-day week after logging sharp drops in worker turnover and absenteeism while largely maintaining productivity.

The vast majority of jobs are likely to stick to the conventional five-day schedule for the foreseeable future. Most companies trying shorter weeks are small employers, not large ones. And some workers in four-day experiments report struggling to get everything done in that time.

Jenise Uehara, chief executive and co-owner of Search Engine Journal, a digital marketing publication that participated in one of the U.S. trials, said she proposed moving to a four-day workweek last year as the company wrestled with growing pains. Some of its three dozen remote employees had become overwhelmed with the increase in work, and turnover was rising.

As part of the experiment, the company declared a “meeting bankruptcy,” wiping all meetings from the calendar for a month, then thinking hard about which were really necessary. Some meetings became shared documents instead, where participants would update each other with progress reports and other notes as they happened.

Within six months, the company’s turnover had dropped, productivity held up, and clients didn’t notice the business had moved to a four-day week, Uehara said. The company plans to continue operating on the four-day week, with staff taking Fridays off.

“We couldn’t keep doing things the same way we’d been doing them,” she said. “We had to figure out a way to work more efficiently.”