Earlier quoted context omitted.
In the Netherlands, if you have a child under 9 years old (it could be 8), your company is required, by law, to let you work 4 days a week if your want. It's actually really common with something like 28% of working men taking a "papadag" ("Daddy day" in English). I wouldn't even consider a job that didn't allow me time to spend with my kids. Money is definitely not the primary driver for a lot of people.
Do you accept a lower salary if you opt to work four days a week?
I don't think a 4 day work week is 20% less productive than a 5 day one, but generally 80% of a full-time salary in this line of work is still more than enough.