What if we only worked four days a week?

Working 4 days a week, would it help with increasing the productivity in a company? In fact in New Zealand a company already have done it, allowing all staff members to work 4 days a week. Read more about it here.

https://www.bbc.co.uk/bbcthree/article/fc8830f5-2e31-445c-a9c0-b1caf06761a3