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Between client calls, meetings, and assignments, it may feel as if every minute of our working week is squeezed to the max. But as it turns out, we are all just procrastinators.

That’s according to research that shows workers can get as much done in a 33-hour week as in 38 hours.

The 2023 report from nonprofit advocacy group 4 Day Week Global—which is the largest of its kind and the first to examine the long-term effects of the four-day week—found that the longer people worked a four-day week, the shorter their workweeks became without output or productivity taking a hit.

Workers could shave five hours off their workweek

Up until now, most studies have examined the short-term effects of working a shorter week.

For example, Britain completed the world’s largest trial of the four-day week, enlisted more than 60 companies, and just fewer than 3,000 workers, to provide feedback on the “100:80:100” working model: 100% pay for 80% of the time, in exchange for 100% productivity.

The results were a 65% reduction in the number of sick days; maintained or improved productivity at most businesses; and a 57% decline in the likelihood that an employee would quit, dramatically improving job retention. But the pilot lasted just six months.

The 4 Day Week Global report examined workers in the U.S., Canada, Britain, and Ireland over an 18-month period. After just six months of working a four-day week, burnout, general health, and job satisfaction improved.

Workers were given a paid day off a week but the same workload to see whether they could get as much done working more effectively—and the study confirmed they could.

Not only that, but unlike previous studies of its kind, the report also highlighted workers could cut their average work time by about four hours, to 34 hours a week, in that time.

This is because workers cut out inefficiencies that a more lengthy workweek allowed, like meetings, to dedicate more time to uninterrupted focus work: Essentially, those of us on a five-day week are filling up our days with time-wasting activities.

Meanwhile, those who continued with the schedule for a year shaved a further hour off their workweek and, as such, reported better work-life balance and a further uplift in their mental and physical health.

Plus it’s not only employees who gained from a shorter week; the four-day week was also an organizational win: Revenue increased by 15% over the course of the trial, weighted in accordance with company size.

It’s probably why no organization expressed a desire to return to five days post-trial, and 89% of workers also wanted to stay with the new four-day plan.

The cons of moving to a four-day week

In theory, shifting to a four-day week looks like a no-brainer for businesses. But in reality, as experts previously warned to Fortune, it’s a logistical nightmare that could make some staff members miserable.

Charlotte Morris, a associate director at ESP Solicitors, explained: “Businesses can’t simply change a person’s contractual terms unilaterally.” Before making any permanent changes, there will be an abundance of contractual changes that must be made with employee buy-in, such as what happens with part-time workers who already work a short week; which day workers will be “off”; and how holiday pay is calculated.

What’s more, although for the most part employees reported an increase in their well-being and work-life balance, for a small minority of employees this was not the case.

“Just like any change, it will suit some and alienate others, and the reality may be that the structure doesn’t suit every employee or business model,” Pierre Lindmark, cofounder and CEO of management consultancy Winningtemp, told Fortune. “The truth is that the four-day working week isn’t for everyone.”

He warned that “one less day at work could lead to increased anxiety and isolation as the result of having the same amount of work to do, but less time to get it done.”

A version of this story originally published on Fortune.com on July 27, 2023.