We already knew workers love a four-day workweek. A U.K. pilot program has found that bosses love it too

That’s the message emerging from the closely watched companies shifting to four-day workweeks in pilot programs run by the nonprofit 4 Day Week Global. A survey out Tuesday finds that 78% of leaders at the more than 70 UK companies that shifted to four-day schedules say their transition was good or “seamless.” Only 2% found it challenging. Most (88%) say that four-day schedules are working well.

The idea of a four-day workweek is no joke. California  lawmakers  recently considered, and then shelved, plans for a statewide four-day workweek for some employees. A survey by Gartner Inc. Found a shorter week to be a favored recruitment and retention strategy.

Six-month pilot programs with over 180 companies are currently underway in a half-dozen countries. Employers typically transition to four-day, 32-hour schedules (with variations depending on role and industry), with no reduction in pay. In the UK pilot, executives at companies with a total of 3,300 employees were surveyed at the halfway point. The program is operated in conjunction with the 4 Day Week Campaign and the think tank Autonomy, along with a data-collection partnership of researchers at Boston College, Cambridge University and Oxford University.

Nearly all of the participating UK organizations (86%) said they’ll likely keep four-day schedules after the pilots finish in November. Almost half, 49%, said that productivity had improved, while 46% said it has remained stable.

“It’s extremely encouraging to see that,” said Joe O’Connor, chief executive officer of 4 Day Week Global, who had expected organizations to show steadier output. “We would see it as a big productivity success if productivity stayed the same.”

Pilot studies are continuing in the UK, US, New Zealand, Australia, Ireland and Canada.

Not all of the organizations that begin the trials complete them, O’Connor said. Roughly 1 in 5 employers drop out, more than half during the pre-planning stage. Executives who have undertaken the pilot studies say that they face the dual challenge of overcoming staff and industry five-day norms alongside the tricky task of removing of improving work processes to get the same output in in four days.

When companies drop out in the planning phase, “The primary reason is the leadership overthinking it and getting cold feet,” O’Connor said. “They start trying to fix every possible problem or issue before they actually run their trial, which is impossible, because a lot of the productivity gains and process improvements are ground up and led by teams.”

He also reports difficulties among companies with cultures of mistrust between leaders and employees.

“They think they’ve got an open, bottom-up style of decision-making, but in practice, that might not be so,” he said.

Growing pains are part of the process.

“It wasn’t a walk in the park at the start, but no major change ever is,” said Nicci Russell, managing director of Waterwise, a nonprofit focused on reducing water consumption. “We have all had to work at it—things like annual leave can make it harder to fit everything in. But the team are pretty happy, and we certainly all love the extra day out of the office.”

Once on four-day schedules, the companies that struggle are often very small and in fields that necessitate five- or seven-day shift coverage, which requires precise scheduling among small numbers of staff. The gift company Bookishly, for example, continues to tinker with staffing during busy times.

Organizations also abandon truncated schedule efforts when hit with unexpected changes, such as new leadership or financial changes. The UK trial participants range across sectors, such as education, media, hospitality and health care, and include Charity Bank, the supply-chain transparency company Everledger, the customer-communication platform Secure Digital Exchange, and the Royal Society of Biology.

O’Connor has learned that when companies don’t need him anymore, things are going well.

“They really need us in the early stages,” he said. “When the demand for contact with us slides, it means they’re well on the road to making this work.”