The four-day workweek is proving to be the gift that keeps on giving.

Companies that have tried it are reporting happier workers, lower turnover and greater efficiency. Now, there’s evidence that those effects are long lasting.

The latest data come from a trial in the U.K. In 2022, 61 companies moved their employees to a four-day workweek with no reduction in pay.

They began it as a six-month experiment. But today, 54 of the companies still have the policy. Just over half have declared it permanent, according to researchers with the think tank Autonomy, who organized the trial along with the groups 4-Day Week Campaign and 4 Day Week Global.

Follow-up surveys help to explain the four-day workweek’s success.