Social mobility or rather Income mobility describes the ability of an individual to move up in the income strata of the society. This is also an indicator of the income elasticity.  As seen in the figure a larger number for this metric shows a smaller chance of being able to move up the income groups based on previous wealth. Surprisingly, there is a higher income inequality in the US and also a lesser chance of changing income strata despite being a developed country.

Social mobility versus income comparison