From Wikipedia
In economics, Hauser’s Law is an empirical observation that, in the United States, federal tax revenues since World War II have always been equal to approximately 19.5% of GDP, regardless of wide fluctuations in the top marginal tax rate.
The theory was first suggested in 1993 by William Kurt Hauser, a San Francisco investment economist, who wrote at the time, “No matter what the tax rates have been, in postwar America tax revenues have remained at about 19.5% of GDP.”
In a May 20, 2008 editorial by David Ranson, the Wall St. Journal published a graph showing that even though the top marginal tax rate of federal income tax had varied between a low of 28% to a high of 91%, between 1950 and 2007, federal tax revenues had indeed constantly remained at about 19.5% of GDP
