This paper by Mark Aguiar and Mark Bils finds that "consumption inequality has closely tracked income inequality over the period 1980-2007":
Has Consumption Inequality Mirrored Income Inequality?, by Mark A. Aguiar and Mark Bils, NBER Working Paper No. 16807, February 2011: Abstract We revisit to what extent the increase in income inequality over the last 30 years has been mirrored by consumption inequality. We do so by constructing two alternative measures of consumption expenditure, using data from the Consumer Expenditure Survey (CE). We first use reports of active savings and after tax income to construct the measure of consumption implied by the budget constraint. We find that the consumption inequality implied by savings behavior largely tracks income inequality between 1980 and 2007. Second, we use a demand system to correct for systematic measurement error in the CE's expenditure data. Specifically, we consider trends in the relative expenditure of high income and low income households for different goods with different income (total expenditure) elasticities. Our estimation exploits the difference in the growth rate of luxury consumption inequality versus necessity consumption inequality. This "double-differencing,'' which we implement in a a regression framework, corrects for mis-measurement that can systematically vary over time by good and income group. This second exercise indicates that consumption inequality has closely tracked income inequality over the period 1980-2007. Both of our measures show a significantly greater increase in consumption inequality than what is obtained from the CE's total household expenditure data directly.
Why is this important? (see also "Is Consumption the Grail for Inequality Skeptics?"):
An influential paper by Krueger and Perri (2006), building on related work by Slesnick (2001), uses the CE to argue that consumption inequality has not kept pace with income inequality.
And these results have been used by some -- e.g. those who fear corrective action such as an increase in the progressivity of taxes -- to argue that the inequality problem is not as large as figures on income inequality alone suggest. But the bottom line of this paper is that:
The ... increase in consumption inequality has been large and of a similar magnitude as the observed change in income inequality.