Does a shorter working week work? What the trials found

The week stopped shrinking

In 1930 the economist John Maynard Keynes predicted that, within a century, rising productivity would let people work about fifteen hours a week. He was right that output per hour would climb. The working week did not follow. Australia's legal standard for full-time work is still 38 hours.

Long hours carry a cost. The World Health Organization and the International Labour Organization estimate that working 55 hours or more a week caused 745,000 deaths from stroke and heart disease in 2016. Against a 35 to 40 hour week, it carries an estimated 35% higher risk of stroke and 17% higher risk of dying from heart disease.

Iceland, 2015 to 2019

Reykjavík City Council and the national government ran trials covering more than 2,500 workers, about 1% of Iceland's workforce. Most moved from 40 hours a week to 35 or 36, on the same pay.

The researchers who reviewed the trials reported that output held steady or improved in most workplaces, and that workers felt less stressed and less at risk of burnout. Unions then negotiated shorter hours, and 86% of the workforce either moved to them or gained the right to.

Read the fine print, though. Iceland cut one to three hours a week in 61 of the 66 workplaces, not a whole day. The later union agreements cut less still. The sociologist Anthony Veal points out that there were no proper control groups in the service workplaces, and that volunteers keen to keep the change may have worked harder to prove it. "Iceland proved the four-day week" goes further than the evidence.

The UK pilot, 2022

From June to December 2022, 61 UK companies and about 2,900 staff moved to a four-day week on full pay. Researchers from Cambridge University and Boston College measured the results.

Measure	Result
Companies still on a four-day week after the trial	56 of 61
Companies making it permanent	18
Revenue over the trial	roughly flat, up 1.4% on average
Staff reporting less burnout	71%
Resignations, against a similar earlier period	down 57%
Sick days, against a similar earlier period	down 65%

Companies volunteered, and many were small and office-based, so the result says more about firms that want to try than about every workplace.

Six countries, 141 organisations

The strongest study so far appeared in Nature Human Behaviour in 2025. It followed 2,896 employees across 141 organisations in Australia, Canada, Ireland, New Zealand, the UK and the US, before and after a six-month move to a four-day week without a pay cut. It also tracked 12 comparison companies that did not change.

• Burnout fell, from 2.83 to 2.38 on a five-point scale.
• Job satisfaction rose, from 7.07 to 7.59 out of ten.
• Mental and physical health improved. The comparison companies showed no such change.

The gains came partly from people sleeping better, feeling less tired and feeling more able to do their jobs. The organisations also reorganised their work before the trial began, to cut wasted time. That is the lesson. Cutting hours works when the work changes too, not when five days are squeezed into four.

What the evidence does and doesn't show

Solid	Not yet shown
Wellbeing, burnout and sleep improve	That every industry can do it, such as shift work, care and manufacturing
Most volunteer employers keep it	Effects over many years
Output holds in the firms that try it	What happens when it is required rather than chosen

Where this leaves you

1. Know the law. In Australia, the Fair Work Act sets maximum weekly hours for full-time employees at 38 plus reasonable additional hours, and you can refuse additional hours that are unreasonable (section 62). Since August 2024 (August 2025 for small businesses), you can also refuse to monitor or respond to contact outside working hours unless refusing is unreasonable (section 333M).
2. Bring the evidence. If your workplace is open to a trial, the published pilots describe how employers prepared and measured output.
3. Measure the work, not the hours. The trials that worked agreed first on what the job had to produce, then let people find the time.