Who would have thought? Four instead of five days of work per week with full salary and the boss thinks that's good too? This is the result of an international pilot study - there are winners on all sides.

After six months of a four-day week with full pay, almost all employees in an international pilot project have drawn a positive conclusion. According to an evaluation of the "Four Day Week" project, 97 percent of around 500 respondents want to stick to the shortened working week and the additional day off.

More than 30 companies with a total of around 900 employees took part in the project, which was accompanied by researchers from Boston, Cambridge and Dublin - mainly from Ireland and the USA, including IT companies, gastronomy, management consultancies and construction companies. According to the survey, two thirds of the companies definitely want to stick to the four-day week with full payment after the six-month test phase, others tend to do so or are still undecided. However, none of the companies stated in the survey that they definitely wanted to return to the five-day week.

According to the study leaders, the reduction in working hours did not result in any cuts in productivity, as companies designed their processes more efficiently: over the six months, company sales increased by an average of 8 percent - compared to the same period in the previous year by as much as 38 percent .

But that's not all: "Physical and mental health improved, as did satisfaction in various areas of life, which may be related to people sleeping better and moving more," said Wen Fan, a Boston College researcher.

Other countries are also experimenting with the four-day week, including Great Britain, Iceland and Belgium. Some German companies are also testing similar models.