So this is what I was doing with all of that graphing. I guess some people might find this useful. I found the information interesting.
A more interesting summary graph is on Wikipedia: Historical tax rates for the highest and lowest income earners.
- U.S. federal individual income taxation 2011
- U.S. federal individual income taxation 2010
- U.S. federal individual income taxation 2009
- U.S. federal individual income taxation 2008
- U.S. federal individual income taxation 2007
- U.S. federal individual income taxation 2006
- U.S. federal individual income taxation 2005
- U.S. federal individual income taxation 2004
- U.S. federal individual income taxation 2003
- U.S. federal individual income taxation 2002
- U.S. federal individual income taxation 2001
- U.S. federal individual income taxation 2000
- U.S. federal individual income taxation 1999
- U.S. federal individual income taxation 1998
- U.S. federal individual income taxation 1997
- U.S. federal individual income taxation 1996
- U.S. federal individual income taxation 1995
- U.S. federal individual income taxation 1994
- U.S. federal individual income taxation 1993
- U.S. federal individual income taxation 1992
- U.S. federal individual income taxation 1991
- U.S. federal individual income taxation 1990
- U.S. federal individual income taxation 1989
- U.S. federal individual income taxation 1988
- U.S. federal individual income taxation 1987
- U.S. federal individual income taxation 1986
- U.S. federal individual income taxation 1985
- U.S. federal individual income taxation 1984
- U.S. federal individual income taxation 1983
- U.S. federal individual income taxation 1982
- U.S. federal individual income taxation 1981
- U.S. federal individual income taxation 1980
- U.S. federal individual income taxation 1979
- U.S. federal individual income taxation 1978
- U.S. federal individual income taxation 1977
- U.S. federal individual income taxation 1976
- U.S. federal individual income taxation 1975
- U.S. federal individual income taxation 1974
- U.S. federal individual income taxation 1973
- U.S. federal individual income taxation 1972
- U.S. federal individual income taxation 1971
- U.S. federal individual income taxation 1970
- U.S. federal individual income taxation 1969
- U.S. federal individual income taxation 1968
- U.S. federal individual income taxation 1967
- U.S. federal individual income taxation 1966
- U.S. federal individual income taxation 1965
- U.S. federal individual income taxation 1964
- U.S. federal individual income taxation 1963
- U.S. federal individual income taxation 1962
- U.S. federal individual income taxation 1961
- U.S. federal individual income taxation 1960
- U.S. federal individual income taxation 1959
- U.S. federal individual income taxation 1958
- U.S. federal individual income taxation 1957
- U.S. federal individual income taxation 1956
- U.S. federal individual income taxation 1955
- U.S. federal individual income taxation 1954
- U.S. federal individual income taxation 1953
- U.S. federal individual income taxation 1952
- U.S. federal individual income taxation 1951
- U.S. federal individual income taxation 1950
- U.S. federal individual income taxation 1949
- U.S. federal individual income taxation 1948
- U.S. federal individual income taxation 1947
- U.S. federal individual income taxation 1946
- U.S. federal individual income taxation 1945
- U.S. federal individual income taxation 1944
- U.S. federal individual income taxation 1943
- U.S. federal individual income taxation 1942
- U.S. federal individual income taxation 1941
- U.S. federal individual income taxation 1940
- U.S. federal individual income taxation 1939
- U.S. federal individual income taxation 1938
- U.S. federal individual income taxation 1937
- U.S. federal individual income taxation 1936
- U.S. federal individual income taxation 1935
- U.S. federal individual income taxation 1934
- U.S. federal individual income taxation 1933
- U.S. federal individual income taxation 1932
- U.S. federal individual income taxation 1931
- U.S. federal individual income taxation 1930
- U.S. federal individual income taxation 1929
- U.S. federal individual income taxation 1928
- U.S. federal individual income taxation 1927
- U.S. federal individual income taxation 1926
- U.S. federal individual income taxation 1925
- U.S. federal individual income taxation 1924
- U.S. federal individual income taxation 1923
- U.S. federal individual income taxation 1922
- U.S. federal individual income taxation 1921
- U.S. federal individual income taxation 1920
- U.S. federal individual income taxation 1919
- U.S. federal individual income taxation 1918
- U.S. federal individual income taxation 1917
- U.S. federal individual income taxation 1916
- U.S. federal individual income taxation 1915
- U.S. federal individual income taxation 1914
- U.S. federal individual income taxation 1913
Notes, sources and caveats
Data is from the Tax Foundation's page U.S. Federal Individual Income Tax Rates History, 1913-2011, which supplied the raw data in MS Excel format.
From 1913 all individuals filed singly. A second filing status for married couples filing jointly appeared in 1949. A third filing status for Head of Household appeared in 1952. A fourth filing status for married couples filing separately appeared in 1971. All four statuses are plotted on all graphs, thanks to a little copying and pasting in the spreadsheet.
The information was then dumped into a text file, and parsed and graphed using Perl.
Almost every year of taxation came with its caveats and special notes, which are listed in the original Tax Foundation data but ignored for the purposes of these graphs due to the extra one-off coding that would have been required. As such, these graphs should be taken to show not absolute truth but only rough trends, and possibly not even that.
The cut-off point for these graphs was USD 250,000. This number was chosen more or less arbitrarily, as a balance between showing behaviour as income tends towards infinity, and still leaving behaviour in the lowest brackets visible. In 2011, tax brackets exist up to more than a third of a million dollars (i.e. off the scale to the right), and historically the largest tax bracket started at USD 5,000,000 (1936 to 1941). Using the supplied Perl, you can modify $maxmoney to recalculate the graphs for any upper limit you wish.
Observations
Income taxation was nominal-shading-to-non-existent until 1917.
Income taxation peaked in 1944 when the U.S. was at the ATM with less than $20 in checking and needed to pay for World War II.
Married people get substantial breaks, as long as they file jointly; married people filing separately are actually punished financially for doing so, compared to e.g. separating and filing singly. However, the differences in absolute terms are smaller now than they were when these new filing statuses were first introduced. In the the late 1980s the differences were negligible in absolute terms.
As seen on Wikipedia, federal individual income taxation rates for the highest earners have rarely been lower than they are in 2011 and are on a downward trend.
There is a concept called the Laffer curve which expresses a relationship between the flat income tax rate and the total income tax collected by the taxing government. A situation with a flat income tax rate would appear on these charts as a single diagonal line with no bracket threshold, meaning the Laffer curve model is very simple. In truth, income tax rate can be a much more complex function of income rather than a simple percentage, even restricting oneself to the piecewise linear, strictly increasing functions seen here. The phase space is not one-dimensional, and optimal taxation curves might be very strange-looking indeed.
Finally, if I may be naïve and sophomoric for a moment, there is no taxation rate below 100% at which people stop wanting more money.
