This Financial Times article has some good numbers describing how the benefits of economic growth over the past few decades have been distributed among U.S. households:
Between 1979 and 2005 the pre-tax income for the poorest households grew by 1.3 per cent a year, middle incomes before tax grew by less than 1 per cent a year, while those of households in the top 1 per cent grew by 200 per cent pre-tax and, more strikingly, 228 per cent post-tax.
The result of this lopsided distribution of income growth was that by 2005 the average after-tax income for the bottom fifth of households was $15,300, for the middle fifth $50,200 and for the top 1 per cent just over $1m.
Looked at from another perspective, in 1979 the post-tax income of the top 1 per cent was 8 times higher than that of middle income families and 23 times higher than the lowest fifth. By 2005 those ratios grew respectively to 21 and 70. The process reached its extreme point with US President George W. Bush’s tax cuts. Emmanuel Saez of the University of California at Berkeley estimates that in the economic expansion of 2002-06 the plutocratic top 1 per cent captured almost three-quarters of income growth.
Figures for wealth, derived from the Federal Reserve Board’s Survey of Consumer Finances, are less up-to-date but the picture is similar. The share of US wealth owned by the top 1 per cent of households rose steadily from 20 per cent in 1976 to 38 per cent in 1998.