The stat you cite is actually 1979, but if you look at the income proportions[1] at that time relative to current by-quintile income proportions, the growth in taxation of the top quintile between 1979 and 2005 is slightly greater than linear with that income growth.
Income growth can definitely explain the increase in tax burden, but my point still stands, no? The tax burden is not shifting from the wealthy to the poor.
And if you look at the bottom quintile, their tax burden has fallen, even though income continues to rise.
Again, not true. Look at the effective tax rates. The lowest quintile pays single digit percentage (negative income tax when you account for the EITC).
Income growth can definitely explain the increase in tax burden, but my point still stands, no? The tax burden is not shifting from the wealthy to the poor.
And if you look at the bottom quintile, their tax burden has fallen, even though income continues to rise.