In the summer of 2022, sixty-one British companies and approximately 2,900 workers participated in the world's largest controlled trial of the four-day work week. For six months, employees worked four days instead of five, at full pay, with no reduction in their contracted hours or salary. The companies were asked to maintain their existing levels of output and service. Researchers from Cambridge University, Boston College and Oxford carefully measured what happened.
The results were striking. Revenue fell in no company. Productivity, measured across several metrics, was maintained or improved in the vast majority of participating organisations. Workers reported dramatically lower levels of burnout and fatigue, higher job satisfaction, and significantly better work-life balance. Sickness absence fell. Staff turnover fell. At the end of the trial, 56 of the 61 companies said they planned to continue with the four-day week. 18 made it a permanent policy immediately.
The 100:80:100 Model
The model being trialled is not a simple compression of five days' work into four — which would merely create longer days and different stress. It is the "100:80:100" model: one hundred per cent of the pay, eighty per cent of the time, one hundred per cent of the output. The claim is that this is achievable because the contemporary working week contains an enormous amount of wasted time: unnecessary meetings, excessive email, administrative tasks that add no value, and the general inefficiency that comes from presenteeism — being at work without doing meaningful work.
"We'd all assumed productivity required the full five days. What we discovered was that most of us were only truly productive for about six hours a day anyway."
Why Some Employers Remain Sceptical
Despite the positive trial results, the four-day week has not swept British workplaces. The majority of large employers remain unconvinced, and their scepticism is not entirely unfounded. The trial participants were, by definition, companies willing to try the experiment — a self-selected group that may not be representative of all employers. Many were in knowledge work, where flexibility is relatively easy to implement; manufacturing, retail and hospitality present different challenges. And the trial lasted only six months — long enough to measure some effects but not long enough to understand how the model performs over years.
There are also sectoral and equity concerns. In the UK economy, workers in precarious, lower-paid employment — cleaners, delivery drivers, care workers — are far less likely to have access to four-day week arrangements, even if the model is proven to work. If the four-day week becomes common only in professional and knowledge-work environments, it could widen existing inequalities between different kinds of work.
The Historical Context
The five-day, forty-hour week is not an ancient institution. It became standard in Britain relatively recently, having evolved from the six-day working week of the Victorian era through a combination of trade union pressure, legislation and the gradual recognition that overworked employees are less productive than well-rested ones. The transition from six days to five was not self-evident, and it was fiercely resisted by employers who claimed it would be economically ruinous. The same arguments are being made today.
Keynes predicted in 1930 that economic progress would eventually allow a fifteen-hour working week by the twenty-first century. We have been economically productive enough to achieve this for decades. That we have not — that productivity gains have instead been taken as income rather than time — reflects choices about how we organise economic life rather than any necessity. The four-day week question is, at its core, a question about what work is for.
What Would Change?
The implications of a widespread shift to a four-day week would extend well beyond individual wellbeing. Transport systems would adapt. Childcare provision would change. The carbon footprint of commuting would fall. The restaurant, entertainment and leisure industries that currently operate primarily at weekends would have three days of increased demand rather than two. The health costs of overwork — which the Health and Safety Executive estimates at billions of pounds annually, including burnout, stress-related illness and cardiovascular disease — would fall.
None of this means the four-day week is straightforward to implement universally. But the evidence from the British trial suggests that, for a significant part of the economy, it is feasible — and that the gains in wellbeing, productivity and staff retention may outweigh the costs of adaptation. The question is not whether it is possible. It is whether we have the collective will to reorganise something as fundamental as the working week.