4-Day Work Week: The Actual Evidence

The 4-day workweek went from fringe pilot to mainstream conversation between 2022 and 2026. Here’s what actually happened in the largest pilots, what the data really says, and what to ask your employer if you’re pushing for one.

The biggest pilots so far

• UK 4DWW (2022, 61 companies): 92% extended the trial. Revenue +1.4% on average. Stress +71% lower; sick days down 65%.
• Iceland (2015-2019, 2,500+ workers): productivity stayed equal or improved. Now 86% of Iceland’s workforce is on shorter hours.
• 4 Day Week Global (rolling pilots, 2023-2026): consistent results across countries: revenue flat or up, retention up, hiring up.

Why it works in practice

• Forces meeting culture audit (most teams cut meetings 25-40%).
• Less context-switching: people batch deep work.
• Recovery is a productivity input, not a competitor to it.
• Selection effect: companies willing to try it tend to be well-managed already.

Where it doesn’t work

• Customer-facing roles requiring 5-day coverage (without rotation overhead).
• Manufacturing / shift work without process redesign.
• Companies that compress 40 hours into 4 days vs reducing hours to 32.

If you’re proposing one

1. Pitch a 90-day pilot, not a permanent change.
2. Define clear outcome metrics upfront (revenue, NPS, deadline hits).
3. Suggest staggered Fridays first (half the team off Fri, half off Mon) to keep coverage.
4. Reference 4dayweek.com’s playbook + case studies.