This is because based on the results of their experiment, which took place for an entire month in August this year, it seems that productivity of employees actually increased by as much as 40%. This means that while employees worked less days, the amount of work that they got done was more than if they had worked that extra day.
The experiment also resulted in employees taking about 25% fewer days off during the month. It also seems that it might be good for the environment because during the month, the amount of electricity consumed went down by about 23%, and about 59% fewer pages were printed, resulting in a potentially smaller carbon footprint while saving the company money as well.
That being said, don’t expect to see Microsoft make it a permanent thing. While feedback to the experiment was extremely positive, with 92% of employees claiming they liked the idea, Microsoft is expected to continue with a regular 5-day work week, although they might bring back the experiment again in the future.