Those who oppose the notion might see productivity as chiefly measured by time — so many minutes equals so much productivity. And that might be true for assembly-line manufacturing, for example; the four-day work week isn’t for every company.
For many other jobs where what’s being created is intellectual property, ideas, strategic plans, sales, marketing, and software, for instance, intellectual acuity is the essential ingredient — and burn-out is a very real challenge in such roles. To be sharp, you need to be well-rested in mind and body. A four-day work week could well boost productivity in that kind of environment.
Even before the pandemic, some companies had begun to loosen up. Casual Fridays became work-at-home Fridays, for instance. Switching to working four days a week seems like a natural progression in that scenario.