AJ, you are conflating the work of Arthur Laffer with supply side Economics, and misrepresenting one of his main tenets.

Laffer did not advocate lowering taxes as a way to stimulate economic growth as a central principle.
He proved empirically and scientificially that there is a level (percentage or proportion) of tax rates beyond which the actual taxes collected will be lower than if the tax rate had been kept at the lower level.
In other words, continually raising taxes can be self-defeating.

Under the socialist labour government in Britain in the 1960's the top marginal tax rate was 83%, plus a 15% "Super tax" = 98% on unearned income.

98 per frikkin cent!

How many people do you think actually paid that kind of tax, and how much super tax was collected?