In my view, understanding the links between greater concentrations of income, variation in spending patterns throughout the income distribution, and the effect of  1  See Congressional Budget Office (2011), Trends in the Distribution of Household Income between 1979 and 2007 (PDF) (Washington: CBO, October).
2  The survey article by Attanasio and Weber (2010) describes several conditions that raise a household's propensity to consume additional income, such as temporary income shocks, borrowing constraints, and low liquidity. However, existing studies do not provide clear evidence that people with permanently low income have a high marginal propensity to consume.