The Evidence So Far

The world's largest trial of the four-day working week, coordinated by 4 Day Week Global and conducted primarily with UK companies, delivered results that have forced business leaders to take the concept seriously. Of the 61 UK companies that participated in the six-month trial, 56 continued with reduced hours after the trial ended, with 18 making the change permanent.

Revenue across participating companies rose by an average of 1.4% during the trial period. Staff turnover fell by 57%. Reported burnout decreased by 71%. These headline figures have generated enormous interest, but UK CEOs considering the four-day week need to understand the nuances behind the numbers.

Where It Works and Where It Does Not

The four-day week is not universally applicable. The trial participants were predominantly knowledge-work organisations where output is not directly tied to hours of availability. Software companies, marketing agencies, and professional services firms reported the strongest results.

Customer-facing businesses with extended operating hours face more complex implementation challenges. Companies cannot simply close on Fridays if customers expect five-day availability. Solutions include staggered schedules, where employees take different days off, or compressed hours, where the same total hours are worked across four longer days.

Manufacturing and logistics companies, where output is directly proportional to operating time, face the most fundamental challenge. However, some have found that the productivity improvements — driven by reduced absenteeism, lower error rates from better-rested workers, and improved morale — partially offset the reduction in total hours.

The Talent Attraction Factor

For many UK companies, the four-day week's most immediate benefit is not productivity but talent attraction. In a tight labour market, offering reduced hours at full pay is a powerful differentiator. Companies that have adopted the four-day week report a 300% increase in job applications and significant improvements in the quality of candidates.

This talent advantage is particularly pronounced in competitive sectors such as technology, where companies compete directly with American firms offering higher base salaries. The four-day week allows UK tech companies to compete on quality of life rather than pure compensation — a proposition that resonates strongly with the millennial and Gen Z workers who now dominate the talent pipeline.

Implementation Challenges

CEOs who decide to trial a four-day week should be prepared for significant implementation complexity. The transition requires rethinking meeting culture, communication norms, and work processes to eliminate inefficiency and protect focused work time.

Most successful implementations begin with an audit of how time is currently spent. Companies consistently find that 20-30% of working time is consumed by unnecessary meetings, duplicative communications, and low-value administrative tasks. Eliminating this waste is the prerequisite for making a four-day week viable.

Change management is equally important. Middle managers often resist the transition, either because they equate hours with commitment or because they struggle to maintain oversight with reduced face-time. Successful implementations invest heavily in manager training and set clear expectations about how productivity will be measured in the new model.

Strategic Considerations for UK Boards

UK boards evaluating the four-day week should consider it as a strategic decision rather than an HR policy. The implications extend to competitive positioning, employer brand, cost structure, and organisational culture.

The most prudent approach for most companies is a structured trial with clear success metrics, agreed in advance, that allow the board to make an evidence-based decision about permanent adoption. The evidence from the UK trials is encouraging, but every organisation is different, and what works for a London marketing agency may not work for a Birmingham manufacturer.