My company did a 4-day work week trial over the summer, with the idea that it was an investigation into how viable it is.

I can't speak for org-wide, but my department had minimal if any impact to productivity.

But now we're back to five days, and the only thing we've heard is that we won't be going to full time four-day weeks, and in fact "that was never on the table".

They're saying we might do 4-day week summers or whatever going forward.

Personally, the 4-day week was so good for my health and well being that if I ever get that opportunity full time I'd trade almost any amount of salary decrease for the shorter week again.

Edit: We constantly see headlines about how mental health issues are on the rise. Constantly people talking about burnout and stress leave and such. I think if we want to combat that, a 4-day work week would be a very good start.

I personally think that it's almost inevitable now, especially with studies like this showing it doesn't impact productivity.