HAPPINESS CHART !!!

We use many project management tools that contain advanced metrics. We can easily pull out various metrics like sprint completion rate, burndown chart,blah-blah etc. Most of the tools and managers don't have any idea about another metric, happiness chart. Yes happiness chart!!. You may be thinking what the f*** is that. I can give an example. In one of my project retro due to my straightforwardness (or ignorance :( ), I told that we need to reduce the stress among team members. Then the manager became suddenly defensive and asked about metrics and what causes the stress among team members. May be out of fever, no team member supported me. But personally, every member of the team complains that there is too much stress. When we push for client happiness and deliverables, we need to take account of the employee happiness also. Then only it will be sustainable. Client, Employee, and deliverables are three pillars of any project. So anyone, any idea? How to take a happiness chart!! What should be its formulae :)