Regulations for salaried and hourly paid workers, industry-specific challenges, and the 24/7 demands of clients and customers all make it unlikely that the practice will spread beyond pockets in smaller companies or within organisations.
"The topic comes up when we talk with companies about flexibility, but when we get down into the details, it's hard to create the arrangement that works for professional organisations," Sladek said.
Still interested in trying? Those who've made the switch to a Monday-to-Thursday schedule - or decided to leave it behind - are the best to turn to for advice.
We spoke with four founders about how they managed a shorter week, and we heard that the biggest challenges are navigating holidays, minimising distractions and keeping up with competitors.
Below, lessons from three small business entrepreneurs who've had success with the four-day workweek - and one who didn't.
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Shawn Anderson co-founded a nearly 50-person tech firm called PDQ.com in what's known as the Silicon Slopes, the tech community around Salt Lake City. It's near some of the best skiing in the country, and he and his twin brother and co-founder Shane Corellian had long given workers half-day Fridays as a perk, in part because the founders wanted it.
But it wasn't really working. "We noticed the half-day Friday people were just phoning it in, and we weren't getting a lot of output," he said. He decided to try a four-day workweek instead.
A year later, Anderson said it's working well, but "it isn't nirvana." With the exception of a receptionist, all his employees get Friday off and work slightly longer days Monday through Thursday. On those days, he's learned to schedule in blocks of break time to keep people productive, cater lunch and not schedule meetings on Thursdays, when everyone is focused on getting out the door.
Still, he made some changes after workers kept calling in sick on Mondays with what he calls the "vodka virus" - or padding existing holiday weekends with extra vacation days. "We can't run the company efficiently in two days or three days" a week, he said, so he now requires people to work on Fridays when there's a holiday Monday and bans extra vacation days during those weeks.
"If you give an inch, people are going to want a foot," he advises. "Don't take it personally."
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Many bosses who offer a compressed workweek expect workers to squeeze 40 hours into four days. But after reading a book called "Deep Work" by Georgetown University professor Cal Newport, Wildbit co-founder Natalie Nagele knew she didn't want to work that way.
After first trying to keep her 30-person software company from working nights and weekends, she took the next leap last year, telling her team she wanted them working only 32 hours over four days. "Our brain's ability to get work done is just four hours a day. If that's true, what are we doing for 40 hours?"
Starting as a summer experiment, she reviewed how her team worked, dropping unproductive meetings, rescheduling others so they didn't interrupt the middle of a morning or afternoon, turning off Slack messaging channels to minimise distractions, and fine-tuning job responsibilities.
Some people expressed anxiety about whether they were getting enough done, and Thursday became "really pressure-filled," Nagele said. She also had to cut back on the vacation time she offered workers - from 25 days of paid time off to 20.
But the adjustments have been worth it. After their first year, Philadelphia-based Wildbit is releasing more products, Nagele said, and she finds she has more time to think about the business. "We might not be writing as many lines of code, but the quality of what we're writing is better."
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When Nate Reusser started running his Roanoke, Ind., design firm on a four-day workweek in 2013, it was all or nothing. The place was closed on Fridays, and employees worked 10-hour days. But as the company hired more people, he realised some didn't like working a 10-hour stretch, and others said the longer day didn't fit with family obligations like school hours.
Now, he runs Reusser Design with a hybrid model, where about 75 per cent of his 16 workers choose a four-day week. One key change has been carving out two-hour blocks of time where employees have no interruptions.
While it works for them, he also admits it has its challenges. "It can be hard when you have a culture split in two - some people don't have that sense of compressed time," he said.
During the holiday season, he lets five-day workers get out earlier. "I think one thing a lot of people [who want to try it] don't understand are some of the scheduling and management things," he said. "I think it's great, but people need to understand some of these safeguards to make sure they maximise their productivity."
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Ryan Carson, founder of Treehouse, which helps companies hire and train tech talent, worked a four-day week for a decade as he built his company into an 85-person firm. But by 2016, as more venture-backed competitors entered the field, he started working more Fridays and realised they couldn't keep up while working less time.
So the Portland, Ore.-based CEO made the tough decision to tell workers they'd have to start working five. "It's simply hard to compete if you're working 80 per cent of the time your competitors are," he said. Working more than his employees also sent an "unhealthy hidden message," he said, and he had to say, "Let's be honest, it's time for us to go back."
Because he'd always paid workers for the equivalent of a full-time salary but required they work only 32, he didn't raise salaries. He cried when telling employees. A few people left.
"It was tough," he said. "People understood that logically, but it's not nice to be told you need to work another day. . . . Leading a company is so much about human psychology."
If he has any advice for others trying it out, he suggests making it an occasional thing that's a fun surprise, such as offering Fridays off for the month of August. "Just think about how everyone talks about their yearly bonus and how people end up complaining if they don't get it," he said. "It's just human behavior to expect it."
