The research surveyed 2,896 workers across 141 companies in six countries – Australia, Canada, New Zealand, the UK, Ireland, and the United States. Participants either moved to a four-day work week or reduced their hours by varying amounts. The study also included a control group of 285 workers in 12 firms who continued working a standard schedule.

Researchers from Boston University and University College Dublin organised the participants into three groups: those who reduced their weekly hours by eight or more (usually switching to a four-day schedule), those who cut five to seven hours, and those who reduced by one to four hours. Over a six-month period, workers completed surveys measuring job satisfaction, burnout, sleep quality, and overall health.

The results were clear. The greatest benefits were observed in those who adopted a full four-day work week, including reduced fatigue, improved mental well-being, better sleep, and higher job satisfaction. Those with smaller reductions in hours also experienced positive effects, although to a lesser degree.

Importantly, the study found no evidence that these improvements came at the expense of productivity. In fact, many workers reported better individual performance.

Researchers emphasised that the way work is structured, especially the opportunity for rest and recovery, can have a major impact on wellbeing. They also highlighted the potential of other flexible models, such as six-hour workdays or 20% reductions in working time.

In Portugal, a six-month pilot project tested the four-day work week in around 40 companies. Nearly 95% of participating firms evaluated the experience positively. Workers reported a better balance between work, family, and personal life, with over 60% saying they spent more time with their families. The trial led to an average weekly working hours reduction of 13.7%.

However, a separate survey by the Portuguese Industrial Association (AIP-CCI) found that 0% of businesses – particularly in sectors like retail, construction, and manufacturing – oppose the introduction of a four-day work week. Among those who support it, 71% believe it should remain optional.