40-hour work-week as a tool of emiserating economic growth

I’m surprised nobody has mentioned France yet. They don’t work a full 40 hour week, as they only work 4 days instead of 5.
I used to work a 4 day week, but 10 hours a day. That extra day was awesome, though I was working Friday nights and saturday mornings (it was either that, or Friday nights and Saturday nights - even worse!).
I really don’t think its some kind of conspiracy to make people buy more.