The 4-Day Work Week Experiment: Results Are In

The 4-Day Work Week Experiment: What the Results Actually Show

The verdict: The largest body of research on the four-day work week, spanning hundreds of companies and thousands of employees across multiple countries, has found that a shorter week with no pay cut improves employee well-being without hurting business performance. Roughly 90% of companies that participated in formal trials chose to continue the arrangement after the trial ended. Revenue stayed stable or grew, burnout fell sharply, and turnover dropped. The model is not without challenges—particularly in customer-facing and shift-based industries—but the evidence is now strong enough to treat the four-day week as a viable workplace intervention, not a fringe experiment.

This article breaks down what the trials measured, what the data actually says about productivity, how different implementation models compare, and what organizations need to understand before adopting a shorter work week.

What the Largest Study Found

In July 2025, the journal Nature Human Behaviour published the largest controlled study of the four-day work week ever conducted. Led by sociologists at Boston College, the study tracked 2,896 employees across 141 companies in six countries—Australia, Canada, Ireland, New Zealand, the United Kingdom, and the United States—through a six-month trial of reduced hours with no reduction in pay.

The design was rigorous. Companies underwent a pre-trial period of work reorganization—eliminating low-value meetings, restructuring workflows, and giving employees more autonomy over how they completed tasks—before the trial began. A set of 12 control companies that did not reduce hours provided a comparison baseline.

The results were consistent across countries and industries. Employees reported lower burnout, higher job satisfaction, and improvements in both mental and physical health. Researchers had worried that compressing five days of output into four might increase stress, offsetting the benefits of the extra day off. That is not what happened. Stress levels fell.

Three mechanisms drove the well-being improvements: better sleep, reduced fatigue, and a stronger sense of "work ability"—the feeling that one can actually do one's job effectively. The study also found a dose-response relationship: employees who reduced their weekly hours by eight hours or more experienced greater improvements in burnout, job satisfaction, and mental health than those with smaller reductions.

The Business Case: Revenue, Retention, and Turnover

The most common objection to the four-day week is that it will hurt the business. The trial data does not support that concern.

The UK pilot, run in 2022 with 61 companies and nearly 3,000 workers, was particularly influential. Almost every company (92%) decided to continue with the four-day week after the pilot. Revenue increased by 1.4% on average, and the likelihood of an employee quitting dropped by 57%. Sick days fell by 65%, burnout by 71%, stress by 39%, and fatigue by 46%.

Notably, employees did not use their extra day off to take on paid work elsewhere. They used it for hobbies, leisure, housework, caring responsibilities, and personal maintenance. Commuting time fell by roughly 30 minutes per week. Men took on a greater share of childcare, suggesting the model may have a modest equalizing effect on unpaid domestic labor.

Iceland: The Longest-Running National Experiment

Iceland offers the most mature evidence base, with trials dating back to 2015–2019 in Reykjavík City Council and the national government. The first trial reduced the working hours of social workers and educators from 40 to 35 hours per week without a pay cut. A second government-led study covered 440 civil servants. In both cases, productivity did not decline, and participants reported improvements in work organization and team interaction. Researchers characterized the results as a "wild success".

By 2025, nearly 90% of Iceland's workforce benefited from shorter working hours. The country's GDP grew by 1.3% in 2025, and unemployment remained low. Comparative assessments indicate that Iceland's economic growth outpaced several European peers, including Germany, Luxembourg, Switzerland, Norway, Belgium, France, Austria, Italy, and Finland.

It is important to be precise about causation here. Iceland's economy also benefited from factors unrelated to working hours. The four-day week trials coincided with a period of broader economic growth. What the data does establish is that the shorter week did not impede growth. The economy did not suffer as a result of reduced working hours.

Two Models, Very Different Implications

Not all four-day weeks are the same. The term describes at least two distinct arrangements, and conflating them is one of the most common sources of confusion in this debate.

Reduced-Hours Model (100-80-100)

Employees work 32 hours instead of 40, with no reduction in pay. This is the model used in the formal trials conducted by 4 Day Week Global and most academic research. The "100-80-100" shorthand means 100% of pay, 80% of time, in exchange for a commitment to 100% of output. This model requires organizations to eliminate inefficiencies and redesign workflows. The well-being and productivity gains in the research literature are primarily associated with this model.

Compressed-Hours Model

Employees work the same total weekly hours (typically 40) but distribute them across four days, usually as four 10-hour shifts. This model does not reduce working time; it compresses it. The benefits are different and generally less pronounced. Longer workdays can be draining, and the model is often used in shift-based industries where coverage requirements make a genuine reduction in hours impractical.

The distinction matters for anyone evaluating trial results. When a study reports "no loss of productivity," it is usually referring to the reduced-hours model. A compressed schedule may maintain output, but it does not deliver the same well-being gains because total work time has not fallen.

Where the Four-Day Week Gets Complicated

The research is encouraging, but it is not universally applicable. The trials that produced the strongest results were disproportionately composed of office-based, professional-services organizations—software companies, marketing agencies, consultancies, and non-profits. These roles have discretion over how and when work is completed, and their output is not tightly coupled to continuous coverage.

Several challenges appear repeatedly in the implementation literature:

• Coverage and customer service. Organizations that need to be available five days a week for clients or the public cannot simply close on Fridays. Some companies that trialed the four-day week ultimately abandoned it because customer service suffered. One trial concluded that a five-day week was "essential" for customers. Offset schedules—where some employees take Monday off and others take Friday—can solve the coverage problem but introduce coordination complexity.
• Workload compression. Employees in some trials reported that the pressure to complete five days of work in four created new sources of stress, particularly in roles with high volumes of reactive tasks. The well-being benefits depend on actual work reorganization, not simply on removing a day from the calendar.
• Middle management strain. The burden of redesigning workflows, managing schedules, and maintaining output often falls on middle managers, who may lack the authority or resources to make the necessary changes.
• A two-tier workforce risk. Office-based professional roles can often adopt a four-day week more easily than retail, manufacturing, or healthcare roles. The Welsh Government's Workforce Partnership Council has warned that this could create a "two-tier workforce" if shorter weeks become a perk available only to certain categories of employees.
• Global coordination. Organizations with international teams or clients reported difficulties synchronizing schedules across time zones when one office operates on a four-day week and another does not.

These challenges are real, but they are not arguments against the four-day week in principle. They are arguments for careful implementation. The trials that succeeded did so because they invested time in preparation—typically several months of work reorganization before the trial began—rather than simply announcing a shorter week and hoping for the best.

How Organizations Make It Work

Across successful implementations, three practices appear consistently:

1. Radically shorten and reform meetings. The average knowledge worker loses two to three hours each day to ineffective meetings, poor technology, and distractions. Eliminating or shortening meetings recovers a substantial portion of the time needed to maintain output in a four-day week.
2. Redesign the workday for focused work. Successful organizations build distinct periods for deep work, collaboration, and administrative tasks. They protect focus time and reduce the fragmentation that makes knowledge work inefficient.
3. Use technology deliberately. Automation, asynchronous communication tools, and better documentation reduce the coordination overhead that consumes working hours.

For shift-based and customer-facing operations, the practical approach is usually a rotating roster. Alba Facilities Services, a Glasgow-based facilities management company, introduced a "gifted day off" model where engineers alternated between Monday–Thursday and Tuesday–Friday schedules, giving each employee one standard weekend and one long weekend in every two-week cycle. This maintained coverage while delivering the shorter week.

What to Watch For If You Are Considering a Trial

The research suggests several design principles for organizations evaluating a four-day week:

• Distinguish between reduced hours and compressed hours. Be clear about which model you are piloting and what outcomes you are measuring. The evidence for well-being gains is strongest for reduced-hours models.
• Invest in reorganization before the trial. The four-day week is a forcing function for eliminating waste, but it only works if the waste is actually eliminated. Companies that simply compress existing inefficient practices into four days will struggle.
• Measure beyond productivity. Track burnout, turnover, sick days, and employee satisfaction. Productivity is difficult to measure in knowledge work, and the business case often rests on retention and well-being rather than output metrics alone.
• Plan for coverage. If your organization has customer-facing or continuous-coverage requirements, design the schedule around those constraints from the beginning. Offset schedules, staggered days off, and rotating rosters are all viable options.
• Be honest about applicability. Not every role can adopt a four-day week in the same way. Acknowledge this and design the policy accordingly, rather than imposing a uniform model that creates resentment or operational failure.

Frequently Asked Questions

Does the four-day work week reduce productivity?

The largest controlled studies found no evidence of productivity loss. Revenue stayed broadly consistent or grew in most participating companies. However, productivity is difficult to measure precisely, and the results depend on the organization investing in work reorganization before reducing hours.

Do employees get paid the same for four days as they did for five?

In the formal trials and the "100-80-100" model, yes. Employees receive full pay for 80% of their time in exchange for a commitment to maintain 100% of output. Compressed-hours models also maintain full pay, but the total hours worked remain the same.

Can the four-day week work in customer-facing or shift-based industries?

It can, but it usually requires a different model. Rotating rosters, offset schedules, and staggered days off are common solutions. The evidence for well-being benefits is strongest in roles with more schedule flexibility, but shift-based organizations have successfully implemented four-day arrangements with careful planning.

What percentage of companies continue the four-day week after a trial?

Roughly 90% of companies across the major trials chose to continue the arrangement after the trial period ended. In the UK pilot, 92% of the 61 participating companies continued. In the largest controlled study, approximately 90% of the 141 companies retained the model.

Is the four-day week legal in the United States?

There is no federal law prohibiting a four-day work week in the United States. Employers are generally free to set schedules as they see fit, subject to overtime regulations and industry-specific rules. Some states and localities have their own requirements, so organizations should verify compliance before implementing a shorter week.

The Bottom Line

The four-day work week is no longer a theoretical idea. It has been tested at scale, across countries and industries, with controlled study designs and long-term follow-up. The evidence consistently shows that a reduced-hours week with no pay cut improves employee well-being—reducing burnout, stress, and fatigue—without the business collapse that critics predicted. Revenue holds steady or grows. Turnover falls. Sick days drop.

The model is not a universal solution. It works best in organizations that can redesign work, eliminate inefficiencies, and manage coverage thoughtfully. It is harder to implement in continuous-operation environments, and it requires genuine investment in change management rather than a simple calendar change.

For leaders evaluating the four-day week, the most useful question is not "Does it work?" The evidence says it can. The more useful question is "What would it take to make it work here?" The trials that succeeded did so because they answered that question before they started.

If you are exploring shorter-work-week models for your organization, the 4 Day Week Global research library and the Autonomy Institute's UK pilot report are useful starting points for understanding implementation pathways.