The 4-day work week debate has moved from philosophy to data. Over 61 companies across 8 countries have now completed formal trials with external measurement. The results are more nuanced — and more positive — than either side of the argument typically acknowledges.
The Iceland Trials (2015-2019)
Iceland's government-run study: 2,500 workers across healthcare, social care, construction, and retail moved from 40 to 35-36 hours per week for 4-5 years.
Results:
- Productivity: Maintained or improved in 93% of workplaces
- Worker wellbeing: Improved across all 8 measured dimensions
- Stress reduction: 30% reported lower stress
- Burnout risk: Reduced significantly in healthcare workers
The trial was so successful that 86% of Iceland's workforce had moved to shorter-hours agreements by 2022.
Microsoft Japan (2019)
A single month-long trial with 2,300 employees, Friday office closings, meeting limits.
Results:
- Productivity: +39.9% (measured by sales per employee)
- Meeting participation: Down 23%
- Electricity consumption: Down 23%
- Paper printing: Down 58%
Caveat: This was one month at a technology company. Short-term trials often show novelty effects that fade.
4 Day Week Global (2022)
The largest coordinated trial: 61 companies, 2,900 employees, 6 months, across US, UK, Ireland, Australia, Canada, New Zealand.
Company outcomes:
- 88% said the trial was "highly successful"
- 91% of companies planned to continue 4-day week after trial
- Revenue: +8.14% average during trial period (compared to same period prior year)
- No company reported revenue decline
Employee outcomes:
| Metric | Change |
|---|---|
| Burnout | -71% reported lower |
| Fatigue | -37% felt less tired |
| Work-life balance satisfaction | +48% improvement |
| Physical health self-report | +54% improved |
| Mental health | +39% improved |
| Resignations | Down 57% vs. prior year |
Where It Works vs. Where It Doesn't
Industries with strong results:
- Software and tech
- Marketing and agencies
- Consulting
- Financial services (back-office)
Industries with mixed results:
- Retail and customer service (customer hours are non-negotiable)
- Healthcare (patient care requires coverage)
- Manufacturing (production lines require consistent staffing)
- Hospitality
The key is output-based work — where it's possible to complete the same deliverables in fewer hours by cutting unproductive activities.
The Productivity Mechanics
The 4-day week typically gains efficiency from:
| Improvement | Estimated time recovered |
|---|---|
| Fewer unnecessary meetings | 3-4 hours/week |
| Higher focus quality (less multitasking) | 2-3 hours/week |
| Reduced presenteeism (not working while sick) | 1-2 hours/week |
| Less time-wasting due to urgency | 1-2 hours/week |
Total: 7-11 hours of recovered productive capacity per person per week — roughly enough to cover the missing day.
Should Your Company Try It?
The honest answer: it depends on your job type. Knowledge work that's measured by output is the ideal candidate. The companies that failed typically had roles where coverage requirements made scheduling impossible.
The safest first experiment: one "no meeting Wednesday" instead of a full 4-day week. If productivity doesn't drop, the 4-day week is likely feasible for your team.
Use the Work-Life Balance Score to assess your team's current health before deciding.