Jonathan D. Fisher and David S. Johnson write,

we show that there has been a large increase in income inequality but no concurrent increase in consumption inequality in the 1990s. Conversely, income mobility and consumption mobility are similar during this time period.

Finally, we link the concepts of inequality and mobility using a social welfare function. The results suggest that income mobility and consumption mobility more than offset the increases in inequality.

I have not paid to access the actual paper, and I have to admit I have at most a vague idea what the last two sentences mean.