Analysis of Hair Coverage

How much hair does a non-bald person have on top of their head. Not the back or the sides, just the top. I know it depends on thickness. But what is the minimum amount of hair needed on top so as to not appear to have thinning hair?

I have told the story of a famous doctor who got a patient with black hair and white skin to allow him to pluck out 50% of hair on one side of his head. With good photos and expert advisers, nobody could tell which side had the hair plucked out. When the skin is darker and the hair is brown or light brown, salt and pepper or blonde, the balding shows less. So what I am telling you is that addressing thinning or hair loss is both a science and an art form, and doctors who have a lot of experience, can help you determine what you need to cover a balding area. I left out other factors as hair shaft thickness (coarse hair) and hair character (curly or kinky hair) which further skew the answer to your question.