The four-day work week has moved from fringe idea to serious policy discussion faster than most workplace reforms in history. Multiple large-scale trials have now completed across the UK, Ireland, the US, Australia, and New Zealand, and the results from the well-designed ones are remarkably consistent.

Not every trial succeeded. But the ones that did share patterns that tell us something important about how work can be restructured without sacrificing output.

The UK Trial: The Big One

The UK’s four-day week pilot was the largest coordinated trial to date. Running from June to December 2022, it involved 61 companies and approximately 2,900 employees. The trial was coordinated by 4 Day Week Global, managed by the non-profit Autonomy, and researched by academics from Cambridge University, Boston College, and University College Dublin.

The results were striking. Revenue across participating companies stayed essentially flat or increased slightly (an average increase of 1.4%). Absenteeism dropped by 65%. Resignation rates fell by 57%. Employee wellbeing scores improved significantly across stress, burnout, and work-life balance metrics.

Of the 61 companies that participated, 56 (92%) chose to continue with the four-day week after the trial ended.

But there are important caveats. The companies that opted into the trial were self-selected — they were already open to the idea and had likely already taken steps toward efficiency. The results don’t necessarily generalise to companies forced into a four-day structure. Self-selection bias is real, and the researchers acknowledge it.

The Australian and New Zealand Trials

Several Australian organisations ran formal four-day week trials in 2024-2025, including financial services firms, tech companies, and a few government agencies.

The Victorian government trial involving select departments found that service delivery metrics were maintained while employee satisfaction increased significantly. Processing times for permit applications, a measurable output, didn’t change. Staff turnover in participating departments dropped to roughly half the rate of non-participating departments.

In New Zealand, Unilever ran an 18-month trial that ended in 2024 and found that reducing hours by 20% led to a 33% reduction in absenteeism and a small but measurable improvement in output per hour. The company made the four-day week permanent for its New Zealand operations.

What the Successful Trials Have in Common

Across the trials that reported positive outcomes, several patterns emerge.

Meeting reduction was non-negotiable. Every successful trial dramatically cut meeting time. Some organisations eliminated all meetings on specific days. Others capped meeting duration at 15 or 25 minutes. One UK marketing firm reported cutting total meeting hours by 60% — and realising that most of the eliminated meetings hadn’t been necessary in the first place.

Asynchronous communication increased. With one fewer day, teams couldn’t rely on “let’s grab five minutes to discuss this” for every small decision. Successful organisations shifted to written updates, documented decisions in shared platforms, and trusted people to read and respond on their own schedule.

Focus time was protected. Organisations that failed at the four-day week often did so because they compressed five days of work into four without changing how time was structured. The successful ones identified core productive hours — usually mid-morning and early afternoon — and protected them from interruptions, meetings, and administrative tasks.

Measurement shifted to output. This is probably the most important commonality. Companies that measured success by hours logged struggled with the transition. Companies that already had output-based measurement systems — or created them for the trial — found the transition much smoother.

The Trials That Didn’t Work

It’s important to acknowledge the failures, because they’re instructive.

Customer-facing service organisations with fixed coverage requirements had the hardest time. A retail store that needs to be staffed six days a week can’t simply close on Fridays. These organisations would need to hire additional staff to maintain coverage while reducing individual hours — which changes the economics entirely.

Organisations with highly interdependent workflows also struggled. If Person A needs Person B’s output to start their own work, and Person B isn’t working on Fridays, the bottleneck effect can slow the entire chain. This is solvable with better workflow design, but it requires significant upfront effort that some trial participants underestimated.

And some trials failed because management didn’t genuinely commit. Telling employees they have Fridays off but then emailing them on Fridays with urgent requests undermines the entire premise. The psychological benefit of the extra day disappears when people feel obligated to monitor their inbox. Companies that work with custom AI development firms have found that automating routine Friday workflows — report generation, data processing, customer notifications — is one way to make the reduced week genuinely stick.

The Economic Argument

Critics argue that reducing work hours by 20% must reduce output by 20%. This seems logical but ignores a fundamental reality: knowledge workers don’t produce output linearly with hours.

Research from Stanford has shown that productivity per hour declines significantly after about 50 hours per week, with sharp dropoffs beyond 55 hours. Working 40 hours doesn’t produce twice the output of working 20 hours. It produces maybe 1.5 times the output, with the final hours yielding diminishing returns.

The four-day week works not by magically making people 25% faster, but by cutting the least productive hours — the Friday afternoon email shuffling, the unnecessary status meetings, the performative presence that adds activity without adding value. When you remove 8 hours of low-productivity time and restructure the remaining 32 hours for focused output, the maths works.

The question isn’t whether the four-day work week can work. The trial data shows it can, under the right conditions. The question is whether your organisation is willing to do the hard work of restructuring processes, cutting meetings, and measuring output rather than attendance. That’s a management challenge, not a productivity one.