5 year averages, centered on year cited.
Original data copied and pasted from here, ample additional information collected by the Concord Coalition, a US deficit hawk group.

Share/All_YT: Data is Year, Individual Income tax share of all income taxes, Corporate Income tax share of all income taxes, and Social Insurance tax share of all income taxes (might not sum to 100% due to rounding, but it happens to do so).

1945    50%    39%    11%    100%
1950    53%    35%    13%    100%
1955    52%    34%    14%    100%
1960    54%    27%    19%    100%
1965    51%    26%    23%    100%
1970    53%    20%    27%    100%
1975    50%    17%    33%    100%
1980    52%    13%    34%    100%
1985    51%    9%    40%    100%
1990    49%    11%    41%    100%
1995    49%    12%    39%    100%
2000    53%    10%    37%    100%

As can be seen, what has happened to the distribution of US income taxes is that individual income taxes have held a relatively stable share, the share of corporate income taxes have fallen by about 3/4, and the share of Social Insurance taxes have about tripled.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.