Two schedules can both be called a “four-day week” and have almost nothing in common. One reduces total time at work. The other rearranges it.
That distinction sounds technical. In practice it decides whether staff get recovery time, whether childcare works, whether overtime bills rise, and whether the benefits seen in the best-known trials are likely to appear in your organisation.
At Day5Group, we help organisations transition to a four-day week, and the first design conversation we have is this one: are we reducing hours, or compressing them?
The two models, plainly stated
A reduced week under the 100-80-100 model means 100% pay, about 80% of previous time, and a commitment to 100% of agreed output. In a typical office that is four eight-hour days, roughly 32 hours in total.
A compressed week means the same total hours in fewer days: four 10-hour days, often written as 4x10, still totalling 40 hours. Staff gain a full day away from work, but each working day is longer.
Both give a third day off each week. Only one reduces weekly exposure to work.
Why the evidence does not transfer automatically
The cases most often quoted for a four-day week are reduced-hours cases.
Perpetual Guardian in New Zealand ran an eight-week trial in 2018, monitored by academics from Auckland universities. Staff worked four days at full pay, output was maintained, stress fell from 45% to 38% of staff reporting stress, and work-life balance scores rose from 54% to 78%. The firm made the model permanent.
Iceland’s public-sector trials, run from 2015 to 2019 and reported by Autonomy and Alda in 2021, cut a 40-hour week toward 35 to 36 hours with no pay cut for more than 2,500 workers. Service and productivity were maintained or improved in most workplaces, while stress, burnout and work-life balance improved.
If your plan is 4x10, you cannot borrow those results and assume they apply. The intervention is different. Longer days change fatigue, commuting pain, and who can pick up children at a normal hour. Shorter total hours change recovery across the week. Researchers who study compressed schedules have long treated them as a separate category for exactly this reason.
Where compressed can still make sense
Compressed schedules are not a mistake in every setting. They can suit services that already work long shifts, staff who strongly prefer fewer commutes, and roles where a longer day avoids a costly handover. Some healthcare and public-safety rosters have used 4x10 or similar patterns for years.
The error is in expectation, not always in choice. If you choose compression, measure it as compression: watch end-of-day fatigue, error rates late in shift, sickness absence, and whether staff with caring responsibilities can actually use the pattern. Do not promise the wellbeing gains reported from reduced-hours trials unless your own data show them.
The practical trade-offs leaders miss
Childcare and school. A day off helps. Ten-hour days can hurt if they push pickup, homework and bedtime into a narrow, exhausted window. Ask carers early, not after the rota is printed.
Fatigue and quality. The ninth and tenth hours are rarely the most accurate. In safety-sensitive or detail-heavy work, that matters more than the calendar gain.
Overtime and law. In some jurisdictions, hours beyond eight in a day trigger daily overtime or extra break duties, even if the weekly total is unchanged. A compressed design that looks free on a spreadsheet can become expensive once payroll rules are applied.
Equity. Office staff may love 4x10. Frontline staff who already stand, lift or deal with the public all day may experience the same pattern very differently.
How to choose
Start from the problem you are trying to solve.
If the goal is recovery, retention and the wellbeing effects seen in Iceland and at Perpetual Guardian, you need a real reduction in weekly hours. Design for 32 hours, define output, and cut low-value work to fund the time.
If the goal is fewer commutes or coverage across longer opening hours, a compressed pattern may be legitimate — with eyes open about fatigue and cost.
If you are not sure, pilot honestly and label it correctly. A mislabelled pilot creates cynicism that follows you into the next change.
Our advice is simple: say reduced when you mean reduced, and compressed when you mean compressed. Your staff, and your data, will thank you for the clarity.
Sources
- Perpetual Guardian trial, New Zealand (2018), academic monitoring by Auckland universities — reported in ScienceAlert, 2018.
- Iceland public-sector shorter-hours trials 2015-2019 — Autonomy and Alda, reported July 2021.
Day5Group is a consultancy that assists in the transition to a 4 day work week. More about Day5Group · All blog articles