Missing Data
A little data might help here. Unfortunately, there really IS no good data on PCE (personal consumption expenditure) and savings stratified by income percentile. There are a couple of surveys, the triennial “Survey of Consumer Finances” by the Federal Reserve and the “Consumer Expenditure Survey” by the Bureau of Labor Statistics, but the self-reported data is laughable. For 2007, the Consumer Expenditure Survey showed a personal savings rate of 18.4%. In the same year, the Bureau of Economic Analysis, which calculates the savings rate as a residual from actual income and expenditure data, showed a savings rate of 1.7%. Either the Consumer Expenditure Survey does a poor job of sampling, or people who fill out surveys are really big liars.
Andrew Kaplan runs some numbers, makes some guesses, which suggest that most Americans are still in negative-savings territory.