The Four-Day Work Week: What Trials Reveal About Time and Output

In 2021, even the BBC reported the “overwhelming success” of four-day week trials in Iceland. Anthony Veal, a business-school researcher at the University of Technology Sydney, replied that the success had been greatly overstated.¹ The report behind the headlines said many workers had moved from a 40-hour week to 35 or 36 hours, yet its own list of workplaces shows most cut one to three hours, and its title spoke of a shorter working week, not a four-day one.²

That gap between headline and method runs through the whole four-day work week debate. Organized trials have now run in many workplaces, and in a 2025 Nature Human Behaviour study that pooled trials from six countries, including the 2022 UK pilot, employees reported the biggest gains in burnout and job satisfaction; output was not measured directly. The firms volunteered, few trials had a comparison group, and nearly every outcome was reported by the workers themselves.³

So when a trial result turns up in the news or in a proposal at work, three checks settle most of it: how many hours the typical week really lost, who chose to take part, and what counted as output. For planning your own week rather than judging a policy, a beginner’s guide to managing your time is the better place to start.

What a four-day week trial changes: hours, pay and how work gets done

Most four-day week trials test a paid cut in hours, not a squeeze of five days into four. In the trials that the non-governmental organization 4 Day Week Global recruited companies for, analyzed by Wen Fan, Juliet Schor and colleagues in 2025, firms had to keep pay the same and offer a meaningful cut in time, but did not have to close on a fifth day. Most still chose a standard four-day week.³

The group, which now sells courses and consulting to organizations making the switch, calls the idea the 100:80:100 model: full pay for 80 percent of the time, while keeping full output.⁴ Compressed hours are a different deal. The UK government describes them as full-time hours worked over fewer days, such as a nine-day fortnight.⁵

The difference matters because the two test opposite things. A compressed week asks whether people can work longer days without harm; a paid four-day week asks whether less total time can produce the same work. A result from one says little about the other, and compressed schedules deserve their own review.

1. Four-day week (100-80-100): four ordinary days, the fifth removed; fewer hours in total, same pay
2. Compressed hours: the same total hours packed into four longer days

There is a third ingredient, and it is easy to miss. The 2022 UK pilot was organized by Autonomy, a think tank, with two four-day week campaign groups, and before it began, organizations had two months of workshops and coaching. Common changes included shorter meetings, less internal email, quiet hours for focused work and automated routine tasks.⁶ A trial therefore tests a package: fewer hours plus a deliberate hunt for wasted time.

Picture a small design agency that closes on Fridays and, in the same month, halves its standing meetings. If deadlines still land, nobody can say which change did the work. Much of that hunt starts with the calendar, and why so many meetings go wrong explains where the wasted hours usually hide. So the first question to put to any four-day week result is which model was tested, and which other changes arrived alongside it.

Did people in the trials really work fewer hours?

Mostly, yes, but by less than a full day. In the UK pilot, the average working week that employees reported fell from about 38 hours to 34. The report’s authors put the shortfall down to firms that cut less than a day and to people who still did some work on their day off, and about one in seven employees said they were working more hours by the end, not fewer.⁶

The reason is ordinary. Clients still email on Fridays, a deadline does not move because the office is closed, and some roles have no one to hand work to. Think of the real drop in hours as the dose of the treatment. A trial where the typical week shrank by an hour or two is testing a much milder version of the idea than its name suggests, and its results should be read that way.

In everyday terms, a four-hour drop is about half a working day. For the average employee in the UK pilot, the change looked more like a free Friday afternoon than an empty Friday. Whether you are reading about a trial or picturing one in your own job, the practical question is who answers the calls that still come in on the day off.

Output: what the UK pilot’s revenue figures can and cannot show

The UK pilot did not measure productivity directly. The organizations tracked such different things that the shared measures were revenue, sick days, resignations and hiring, and revenue stayed broadly flat across the trial among the organizations that supplied figures, fewer than half of the total. A comparison with an earlier period showed a much larger rise, but the report itself notes that firms stayed exposed to outside factors such as the economic climate.⁶

Revenue is a blunt proxy for output. It moves with prices, seasons, big contracts and the wider economy, so a jump against last year may say more about which firms were growing than about their schedule. Take a small accounting practice that stops working Fridays and keeps its revenue flat: it may have worked faster, raised its rates, dropped small clients or simply had a busy quarter, and the revenue line looks the same in every case. When the organizations were asked how productivity had been affected, the average rating was positive: a judgment by the firms that chose the policy, not a measurement.⁶

Myth

Four-day week trials proved that productivity goes up.

Fact

Most trials tracked revenue, service levels or firms' own ratings; few measured output per hour directly, and a 2024 systematic review called the productivity effect inconclusive.

The wider research agrees. A systematic reviewsystematic review: A review that fixes its question and its rules for including studies in advance, then searches out every study that fits and weighs them together. Some systematic reviews pool the results into a meta-analysis; others describe what the studies found without combining the numbers.Full entry in the glossary of 31 academic articles on four-day weeks, published by Timothy Campbell in Management Review Quarterly, found the effect on productivity inconclusive.⁷ The lesson: “revenue held steady” is not “output per hour rose”, and “the firm was pleased” is not a measure of either.

Four-day work week trials and wellbeing: the most consistent finding

Employees in four-day week trials consistently reported feeling better, and the strongest evidence comes from Fan and colleagues’ 2025 study, which compared staff at trial companies before and after with staff at a small group of companies that kept a five-day week. It is a quasi-experimentalquasi-experimental: Describes a study that compares a group that got something with a group that did not, where the researcher did not do the assigning: a policy, a rollout or people's own choices did. Because the groups were not formed at random, they may have differed before it started.Full entry in the glossary design: a comparison group, but no random assignment.³

The study

Limited evidence

Six months on four days: 141 volunteer employers set against 12 that kept five

Average weekly hours in trial companies fell by about 5 over six months. Employees reported less burnout, higher job satisfaction and better self-rated mental and physical health, changes the authors describe as small to medium; staff at the comparison companies, whose hours stayed at about 39 to 40, showed no such change.³

A small-to-medium change is one a team would notice in how people talk about their week, not a transformation. The authors say plainly that this was not a randomized trialrandomized controlled trial: A study that assigns participants to the treatment or the comparison group at random, so the groups start out alike and a difference in what happens next can be put down to the treatment. Random assignment makes the two groups comparable; it does not make the people in the trial representative of anyone else.Full entry in the glossary, that senior managers chose to join, and that the results probably overestimate the effect for a typical employer. Why would fewer hours help? In their analysis, the gains were linked mainly to three reported changes: feeling more able to do the job, fewer sleep problems and less fatigue. People whose own hours fell the most reported the biggest improvements, and the gains were still there at a year. All of these outcomes are self-reportedself-report: A measure in which people describe their own behavior, feelings or circumstances, usually by answering a questionnaire. When the same person supplies both of the things being compared, shared habits of answering can make the link between them look stronger than it is.Full entry in the glossary, which is why how burnout is defined and measured matters when you read them.³

The only randomized evidence comes from shorter hours, not a four-day week. In a Swedish public-sector study run in 2005 and 2006 and published in 2017, workplaces were assigned at random, and staff whose hours were cut by a quarter on full pay recorded better sleep and less stress in sleep diaries over 18 months, with small effects.⁸ Those workplaces were funded to hire extra staff, so nobody had to fit the same work into fewer hours, the very thing four-day week firms attempt. A 2022 systematic review of such studies, most in health care, linked paid cuts in hours to better sleep and less stress, with unclear effects on self-perceived health.⁹

Here is what the pattern looks like in a normal office. Two colleagues get the same Friday off. One leaves the laptop shut; the other clears the inbox every Friday morning to stay ahead. On the pattern in Fan’s data, where bigger cuts in a person’s own hours went with bigger reported gains, the first would be expected to feel more of the benefit than the second. If you are offered a shorter week, the part worth guarding is the time off itself.

What Iceland’s trials tested, and what critics said

Iceland’s trials, run by Reykjavík City Council from 2015 to 2019 and by the national government from 2017 to 2021, cut the week by a few hours on full pay rather than removing a day, and reported that service held steady while wellbeing improved. They included offices, playschools, care services, a police station and a hospital department. The government trial also set up comparison workplaces that kept their usual hours, and applicants named the service measures they would track, such as the processing of immigration applications. Output was judged by whether service held, not by output per hour.²

Veal made three objections in 2021: the trials never tested a four-day week, the cuts were small (one to three hours a week in 61 of the 66 workplaces, by his count), and the work units volunteered, so staff may have been motivated to make it work. He also notes that the private-sector agreements that followed cut the standard week by well under an hour.¹

That puts the report’s most quoted number in context: about 86 percent of Iceland’s workforce, it says, had since moved to shorter hours or gained the right to negotiate them. The report was co-published by Autonomy and Alda, an Icelandic group that has advocated shorter hours since 2011.²

Spread over five days, even the largest cuts in the report’s tables, four or five hours, come to about an hour a day, and most were smaller: a later start or an earlier finish, not an empty Friday. That is a real change on a hospital ward or at a police station, and the report says services absorbed it, but it is a milder test than losing a whole day.² Before you pass on an Iceland story, or any trial result, open the report and check its title and the hours before and after.

Why the design of the trials limits what they prove

Four-day week trials share three design limits: the organizations volunteered, few had a comparison group, and nearly all outcomes were reported by employees. Each can make the results look better than a typical employer should expect. The 2025 study had a comparison group, yet its authors still flag the other two limits.³

Volunteering works like judging a diet only by the people who signed up keen. A firm joins because its leaders already believe in the idea, and it has every reason to make the change succeed. Without comparison firms, a before-and-after result also absorbs whatever else was going on: the UK pilot ran during a period the report says was popularly known as the Great Resignation, when many workers were quitting.⁶

Self-report adds a third layer. Employees who like a new schedule have a stake in keeping it, so their answers may lean hopeful. Fan and colleagues offer one check against blanket over-reporting: satisfaction with time rose far more than satisfaction with other parts of life, the pattern you would expect if the shorter hours were doing the work.³

Much of the public case also rests on its advocates’ own reports, Campbell’s review notes; the academic studies it gathered were mostly favorable but also found tighter performance monitoring, scheduling problems and benefits that may fade.⁷

Persistence is the most practical signal the trials offer. A year after the UK pilot, almost nine in ten of its organizations still ran the policy, according to a follow-up by the same organizers.¹⁰ A firm losing money on the schedule would have reason to drop it, but these were enthusiasts, and a follow-up cannot say how the policy would fare in firms that never wanted it.

The bottom line

Four-day week trials show fairly consistently that people who work fewer paid hours report feeling better, and that most of the organizations that volunteered kept the policy. They do not yet show how output changes for a typical employer, because the firms chose themselves, few trials had comparison groups and output was rarely measured directly. Read each new result by asking which schedule was tested, how many hours actually disappeared, and compared with whom.