Some companies have moved to a four-day working week on full pay.

Some companies have decided that their employees will work only four days a week but receive the same salary. This idea has clear advantages, but there are also problems.

The main advantage is rest. A person who has three free days can sleep properly, spend time with his children and do sport, so he returns to the office on Monday with much more energy. Many companies which tried this system reported that the employees did the same amount of work in four days, because they were less tired and they wasted less time.

Another advantage is that it is easier to find good workers. If two companies offer the same salary but one offers a free Friday, everybody chooses the second one. Employees also stay longer in this company, so the company saves money on training new staff.

On the other hand, this system does not work everywhere. A hospital needs nurses seven days a week, and a factory machine must produce every day. In these places, the company must employ more people to cover the fifth day, and this is very expensive.

In addition, sometimes the work is not reduced, only compressed. If an employee must finish the same tasks in four days, he works ten or eleven hours each day and comes home exhausted, so the benefit disappears.

In conclusion, a four-day week gives employees more rest and helps companies attract good staff, but it is impossible in some sectors and it can simply make the working days longer.

A number of employers have adopted a four-day week without reducing pay. The results reported have been encouraging, though they depend heavily on the kind of work involved.

The strongest advantage is that rest improves the quality of the hours worked. Concentration is finite, and a substantial portion of a conventional week is consumed by meetings that exist because time was available and by tasks performed slowly because there was no reason to hurry. Where output depends on judgement rather than on presence, removing a day frequently removes the least productive one, and trials have repeatedly found output maintained rather than reduced.

The second advantage is in recruitment and retention. An extra free day is a benefit competitors find difficult to match without matching the policy itself, and it is particularly valuable to employees with caring responsibilities. Lower turnover then saves recruitment and training costs that rarely appear in discussions of what the policy costs.

The principal disadvantage is that it cannot be applied everywhere. Hospitals, care homes, transport and retail require coverage across the week, so the only way to shorten individual hours is to employ more people — a genuine cost rather than an efficiency gain. Manufacturing tied to continuous processes faces the same constraint.

A further risk is compression rather than reduction. If the same workload is simply redistributed into four days, employees work ten-hour days and arrive at the third day off already exhausted, which delivers none of the recovery the policy was intended to produce.

In conclusion, a four-day week works well where output is measured by results rather than by hours, but it is difficult to extend to essential services and risks lengthening days rather than shortening weeks.

The four-day week on full pay appears to promise something impossible — the same output from fewer hours — and the reason it is not impossible tells you exactly where it works. In a great deal of professional work, output is not proportional to hours present; a significant share of the week is absorbed by meetings that exist because time existed to fill, and by tasks expanding to occupy the space allotted. Remove a day and much of what disappears was never producing anything. Where that slack exists the policy is close to free; where it does not, it is simply a pay rise for less work.

The clearest advantage follows from this. Attention is a finite resource, and rested employees do better work in the hours they are present, so organisations trialling shorter weeks have repeatedly reported output maintained rather than reduced. There is a secondary effect too: a compressed week forces genuine prioritisation, and meetings that survive that scrutiny tend to be the ones worth holding.

Recruitment and retention supply a second, more measurable benefit. An additional free day is difficult for a competitor to match without adopting the policy outright, and it is disproportionately valuable to employees with caring responsibilities — many of whom would otherwise have reduced their hours and their pay. Lower turnover then avoids recruitment and training costs that are rarely counted when the policy's expense is estimated.

The decisive disadvantage is that the enabling condition is absent across much of the economy. In nursing, care work, transport, retail and continuous manufacturing, output is directly hours-bound: a ward cannot be covered by a better-rested nurse who is not there. Shortening individual weeks in those sectors requires hiring proportionally more staff, which is a straightforward cost — and, given existing shortages in exactly those occupations, frequently not achievable at any price.

This produces the objection I find most serious. If the policy spreads only where it is cheap, it will accrue to office workers who are already comparatively well paid and already have some control over their time, while nurses and shop workers continue on five days. A reform that improves conditions for the advantaged and cannot reach the rest is not neutral in its effects, whatever its intentions.

Finally, the compression risk deserves stating as a design failure rather than an inevitability. Where the same workload is simply redistributed into four ten-hour days, employees reach the extra day too depleted to use it, and the recovery the policy exists to deliver never occurs. That outcome is common, but it reflects organisations adopting the schedule without doing the harder work of removing tasks — which was the actual mechanism all along.