What do you mean when you say employee happiness? Because this list is pretty much what I'd reckon constitutes employee happiness.
https://www.nytimes.com/2018/04/24/business/china-women-tech...
Some people just want to sit for 8 hours, go home, and watch football.
This list jives with the internal motivators that appear to drive really great work above the survival level: safety, opportunity and recognition.
Could be 8 because of hours and location.