Impactism
日本語 Join Impactism
Manifesto The Impact Standard Foundations Objections Read For organizations 日本語
Join Impactism
Sunlight falling across an empty desk beside a window
Photo by Alexander Holmes on Unsplash

Essay

The Four-Day Week: What the Evidence Shows

September 21, 20269 min read

A four-day week means cutting the working week by about a day and not cutting anyone’s pay. Not four longer days. Fewer hours, same salary. It has been tried now in Iceland, the United Kingdom, Ireland, the United States and several other countries, and the findings run one way. Burnout falls, and output holds. That is a real result. It is also thinner than the headlines make it sound, because almost every trial was run by employers who put their own hand up.

The strongest evidence runs across six countries and one Icelandic decade. The most interesting document in the whole literature is a Japanese Cabinet decision from 2021 that almost nobody outside Japan quotes.

The largest study so far

The strongest single piece of evidence is a paper published in Nature Human Behaviour in 2025 by Wen Fan, Juliet Schor, Orla Kelly and Guolin Gu. It pooled before-and-after data from 2,896 employees at 141 organisations in Australia, Canada, Ireland, New Zealand, the United Kingdom and the United States. Each organisation spent time reorganising its own work before the trial started, then ran six months on a four-day week with no reduction in pay (Fan, Schor, Kelly & Gu 2025).

Burnout fell. Job satisfaction rose. Self-reported mental and physical health both improved. The authors checked the result against twelve companies that stayed on five days, and the same pattern did not show up there. Three things carried most of the effect. People said they could work better, they slept better, and they were less tired.

The gain did not arrive through a new tool or a cleverer process. People were less tired, so they worked better and felt better.

The UK pilot

The trial most people have heard of ran from June to December 2022. Sixty-one British organisations and around 2,900 workers took part, coordinated by 4 Day Week Global and studied by researchers at Boston College, the University of Cambridge and the Autonomy Institute. The report came out in February 2023 (Autonomy 2023).

Revenue across the responding organisations rose 1.4% on average over the six months. Staff departures fell 57%. Seventy-one per cent of employees reported less burnout, 39% less stress. When the pilot ended, 56 of the 61 organisations kept going, and 18 said the change was permanent.

The revenue figure deserves a flat reading. These companies gave up roughly a fifth of their scheduled hours and ended six months about where they started. That is the claim that survives scrutiny, and it is smaller than the one people quote.

Iceland, which was not a pilot

Iceland is different in kind, and it is the case most worth studying. Between 2015 and 2019 Reykjavík City Council and the national government cut the working week from 40 hours to 35 or 36 for about 2,500 public sector workers, with no cut in pay. That is over 1% of the country’s entire working population, and it covered hospitals, preschools, offices and social services rather than software firms (Alda & Autonomy 2021).

Productivity and service delivery stayed the same or improved in most workplaces. The trials were revenue neutral for both the city and the state. Icelandic unions then took the results into national wage bargaining, and 86% of the country’s workforce has either moved to shorter hours or won the right to negotiate for them.

Iceland is the closest thing to a real answer anyone has, and it still is not a controlled experiment. Nobody randomised a nation.

What the evidence does not support

Every trial listed above recruited organisations that wanted to be in it. A firm that volunteers for a four-day week is a firm that already suspects it can afford one, run by managers who want it to work and staffed by people who will report that it did. That is selection, and it is not a small problem. The 2025 paper is the only one with a control group at all, and that group was twelve companies, chosen by the same process.

Most of the outcomes are self-reported. Burnout, sleep, work ability and satisfaction are all things the same person answers about themselves twice. Six months is short. And the work reorganisation that happens before the trial is part of the treatment, so nobody can yet separate the effect of shorter hours from the effect of a company finally cancelling its useless meetings.

The honest summary is narrow. In self-selected, mostly white-collar organisations that prepared first, cutting the week by a day improved how workers felt and did not visibly damage output over six months. That is worth knowing. It is not proof that a country can do this, and it says almost nothing about a hospital ward, a warehouse or a farm.

There is also a distributional problem sitting under all of it. The organisations that can run a four-day week are the ones whose output is not tied to a machine, a ward or an opening time. A software company can cancel Fridays. A ward cannot, because the patients are still there on Friday, and a shop that closes a day loses a day of trade. So the people most likely to be offered this are people who already have some room, and the people with the least of it, on shifts, on hourly pay, in care work, are the last in the queue. Any honest version of this argument has to say that out loud.

What Japan did with the idea

Japan’s version is easy to miss in English, and it is more interesting than the trials.

On 18 June 2021 the Cabinet adopted its annual Basic Policy on Economic and Fiscal Management and Reform, and put an optional three-day weekend into it. The sentence is worth reading in full: 「選択的週休３日制度について、育児・介護・ボランティアでの活用、地方兼業での活用などが考えられることから、好事例の収集・提供等により企業における導入を促し、普及を図る」 (Cabinet Office 2021). Roughly: because an optional three-day weekend could be used for childcare, for nursing care, for volunteering and for a second job in a rural area, the government will gather good examples and encourage companies to adopt it.

The state named childcare, nursing care and volunteering as the uses of the free day. It did not name rest, and it did not name output.

That is a policy document written by a finance ministry, and it lists volunteering as a reason to work less. No four-day-week trial anywhere measured that outcome, because no trial thought to ask.

We would rather be clear about one thing the policy is not. The Cabinet did not require anything. It said the government would collect good examples and encourage firms to take them up. That is the weakest instrument a state has, and eighteen months of encouragement moves fewer companies than one line of binding law. What it did do was put an official Japanese name on the arrangement, which is why every prefectural scheme since has had something to point at.

Tokyo then did it to itself. On 12 February 2025 the Tokyo Metropolitan Government put a bill to its assembly amending the ordinance on staff working hours, holidays and leave, introducing a four-day week through flexitime for metropolitan employees from 1 April 2025 (Tokyo Metropolitan Government 2025). The employer here is a prefectural government, and it moved first on its own staff rather than on the private sector.

Why we care, which is not productivity

Almost everything written about the four-day week is an argument with a chief financial officer. Does output hold, does revenue hold, can we afford it. In 1930 John Maynard Keynes looked a century ahead and predicted a fifteen-hour week, then admitted that the free time would be the harder half of the problem rather than the prize (Keynes 1930). The wealth arrived roughly as he guessed. The hours did not fall anywhere near that far, and we have written at length about where the dividend went in What Keynes Promised Us.

A four-day week is the first serious institutional attempt in decades to take a slice of that dividend as time instead of as things. That is what makes it worth watching, whatever the revenue numbers do.

And time is the cheapest slack a society can hand a person. A floor under incomes takes tax, politics and years. An hour back on a Wednesday takes a scheduling decision. We have argued that 余裕, the room to breathe, is the precondition for living by anything other than money, because a person with no room has nothing to look up from (Room to Breathe). A day is a lot of room, and it can be handed over by a single employer in a single quarter.

What the day is for

A shorter week is not a yardstick. It does not tell anyone what a life is for. It buys back a Friday, and a Friday can go to a golf course, a second job, or an afternoon spent with someone who has nobody else coming. Nothing about the policy decides which.

The Japanese Cabinet’s list is the only official document in this whole literature that took a position, and it took the right one. It named care and volunteering, and it named them first.

A finance ministry wrote that list, and it is a claim about culture rather than about output. Capitalism stays, and it keeps making the wealth. What a society admires is a separate question, and most of the time nobody answers it on purpose. If the four-day week spreads and the freed day goes entirely to consumption, we will have bought some rest and changed nothing else. If it goes even partly to the people around us, something else happens, and no trial will pick it up because no trial is measuring it.

Make impact, not money, the measure of a life.

Sources

← All essays

Impactism is free — no paywall, no membership fee, and it will stay that way. If this argument was worth your time, donations are what pay for it. One-time or monthly, any amount.

Support the argument