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, 1979–2007” [Excel spreadsheet]. Cumulative growth is calculated by dividing the average capital income in the base year (1979) into average capital income in each subsequent year (1980–2007). Average capital income by income group is calculated by multiplying the share of capital income 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; see Table 2.4 notes for explanation of capital income. Data are inflated to 2011 dollars using the CPI-U-RS, and then indexed to 1979=0.