Until some affective connection between macroeconomic policy changes, e.g., tax rate change, and microeconomic activity the Lauffer Curve remains in the same intellectual sphere as Astrology.

Just to ensure we're both on the same page: What do the variables reference in your equation?  

And for 3 PN points ....

Is that a conditional or identity equals sign?  ;-0

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre