A common critique of most measures of income inequality, which are based on a single year's income, is that they fail to take account of income mobility. If income fluctuations are large, and individuals can smooth consumption, then high inequality and high mobility may be no worse than low...

Different economic characteristics between developing and developed countries may require worker with different skills, resulting in different returns to the same ability. Moreover, it is also possible that different countries require different skills depending on their economic fundamentals....