Documentation and methodology
Underlying data are from the Congressional Budget Office Average Federal Taxes by Income Group, “Sources of Income for All Households, by Household Income Category, 1979 to 2007” [Excel spreadsheet]. Cumulative growth is calculated by dividing the average wages in the base year (1979) into average wages in each subsequent year (1980–2007). Average wages by income group are calculated by multiplying the share of wages by the average pretax income in each income group. See Figure 2M notes for calculations of the 80th–<90th percentile, 90th–<95th percentile, and 95th–<99th percentile. Data are inflated to 2011 dollars using the CPI-U-RS, and then indexed to 1979=0.