The world's largest trial of a four-day week ended this week - and 92% of the companies that participated plan to continue with the truncated work schedule because the benefits were so clear.

The study of 61 UK-based companies and about 3,000 employees delivered results that are largely consistent with existing evidence from other studies, "further demonstrating the benefits of reduced-hour, output-focused working," the study concluded.

After the trial, 56 of 61 companies are continuing with their four-day week. Only two companies said they are "definitely not" doing so, while others three expect to continue, but have not confirmed it.

The pilot program was conducted by the nonprofit 4 Day Week Global, the UK's 4 Day Week Campaign and Autonomy, a think tank. It guided the companies and their workers through a six-month test of a 32-hour, four-day week, with no loss of pay for employees. Including a previous study of companies in US and Ireland, a total of 91 companies with about 3,500 workers completed pilot programs of a shorter work week.

In addition, 75 companies and 1,751 employees completed surveys, which led to the latest findings.

Companies rated their overall experience with an average of 8.5/10, with business productivity and business performance each scoring 7.5/10. Remarkably, corporate revenue - weighted by company size across respondent organizations - remained mostly the same over the trial period, rising by 1.4% on average. When compared to a similar period from previous years, organizations reported revenue increases of 35% on average, an indication of healthy growth during the work time reduction.

"Some of the most extensive benefits of shorter working hours were found in employees' well-being," the study concluded. "Before and after data shows that 39% of employees were less stressed, and 71% had reduced levels of burnout at the end of the trial. Likewise, levels of anxiety, fatigue, and sleep issues decreased, while mental and physical health both improved."

While both men and women benefit from a four-day week, women's experience is generally better, the study said.

"This is the case for burnout, life and job satisfaction, mental health, and reduced commuting time," said Dr. Dale Whelehan, a behavioural scientist and CEO of 4 Day Week Global. "Encouragingly, the burden of non-work duties appears to be balancing out, with more men taking on a greater share of housework and childcare."

The number of people quitting companies during the study decreased significantly, dropping by 57% during the trial. Additionally, 15% of employees in participating companies indicated no amount of money would induce them now to accept a five-day workweek over a four-day one.

"For many, the positive effects of a four-day week were worth more than their weight in money," the report said.

According to a 2022 global survey of 3,600 employees by Gartner Research, a 4-day workweek appears to be the most popular attractor among "new and innovative benefits to recruit talent."

Additionally, 63% of candidates selected "4-day work week for the same pay" as a top five benefits that would attract them to a job (this number jumps to 74% for respondents in the US), according to Gartner.

"Looking ahead, organizations seeking to distinguish themselves in today's new talent landscape will continue to adopt a human-centric work design -where employees are seen as people, not just resources -and give employees the autonomy, flexibility and freedom to integrate work into their lives the best way they see fit," said Caitlin Duffy, director in Gartner's HR practice.

However, few organizations are piloting or implementing a 4-day work week. As of late June 2022, only 16% of organizations polled were considering a 4-day work week and only 5% had implemented it.

Boston College Professor Juliet Schor, the lead researcher in the 4-Day Work Week study, said the results were mostly the same, regardless of a company's size, "demonstrating this is an innovation which works for many types of organizations.

"There are also some interesting differences," Schor said in a statement. "We found that employees in nonprofits and professional services had a larger average increase in time spent exercising, while those in construction/manufacturing enjoyed the largest reductions in burnout and sleep problems."

Other key business metrics showed signs of positive effects. In addition to slightly higher revenues and fewer people quitting, there was also a 65% reduction in the number of sick days taken by employees.

Not everyone was convinced by the findings.

Charlotte Morris, associate solicitor at esphr - a self-described "new-model employment law firm" - said while there's "no doubt" about benefits of a shorter week with full pay for employees and and staff retention and recruitment, for some businesses it could be a headache. She also said the six-month pilot was not long enough to determine the long-term benefits of a 32-hour work week.

For example, Morris said, companies would have to figure out what day of the week employees don't work, what happens with part-time workers who already work a short week, how holiday pay entitlement is calculated, and what contractual changes are needed. "Businesses can't simply change a persons's contractual terms unilaterally," she said. 

"It's interesting to finally see results from a trial done at some length," Morris said via email toComputerworld. "Arguably though, given the prolonged period of time we work for, from leaving education to retirement age for most, a six-month trial is still not long enough to truly measure the impact a shorter working week will have. Therefore, results must be taken with a degree of caution."

Environmental outcomes from the study were also encouraging, with commute time falling across the full sample by a half hour per week.