This doesn't really show much besides the fact that for many European Countries they don't suffer from the same form of income inequality as we do. Note that Japan is ranked 15 yet is one of the worst examples of this. The Social Index tells nothing of the lives of the people in these countries.

In Japan you have to be admitted into a high school program and from their the trajectory of your life starts. All the way into the College process. It's not a fair system yet it's ranked 15.

In Europe, it's easier for someone from the 20th percentile of income to break into the 80th percentile of income. The type of social mobility GP seems to be talking about is escaping the "working class" into the modern equivalent of the aristocratic class (8 figure net worth).

Your link proves that european countries are close to US. Some better, some worse.