This just in! Supply-side economics is wrong!
But seriously folks, does anybody really believe that folks will work more and spend more (and thus boost GDP) because their taxes have been cut? These idiotic voodoo economists (Poppy Bush at least got this much right about the supply-siders) have been romanced by their own abstractions and ideology. Homo economicus is the pathetic two-dimensional silhouette of an actual human being who animates liberal economic models. He has perfect information, complete free will and always wants more and more and more (if the price is right). Some economists remember that this little fellow doesn't actually exist, but somehow those devoted to voodoo apparently forgot this point in moving from models to the real world.
It turns out that, low and behold, most workers don't actually control the hours they work. Who woulda thunk it? So cutting taxes doesn't mean John Q. Public puts in another 5 hours a week at the office instead of throwing back cold ones in his Lay-Z-Boy because the boss decides when John works, not John. It's all well and good for economists to study cab drivers and major-league baseball game vendors and bicycle messengers to figure out whether people do or do not respond to incentives the way the voodoo economists think they will, this is at the margins. Middle class workers on salary don't get more money for more work, and working class folks on the time clock rarely get to decide when to work and when not to. They might work more, but working less is not an option.
Let's see voodoo economics for what is really is -- a lie designed to hide the truth that the rich get richer, they stick the middle class with the bill, and squeeze the poor for every dime they're worth.