Why you can't soak the rich

The WSJ has a editorial about an interesting calculation from San Francisco investment economist Kurt Hauser (which they suggest calling Hauser's law):

No matter what the tax rates have been, in postwar America tax revenues have remained at about 19.5% of GDP.

The point being that a tax rate hike reduces GDP (which is agreed up by everyone) but it will lower tax revenues. The Journal notes the similarity to the Laffer curve but this seems wholly independent.