Supply side , or Trickle Down is a great deal more than simply "allowing" people to spend and invest their own money. Every economic structure "allows " people to use their own money as they see fit. Trickle down concentrates wealth with the supplier , and removes the wealth in large amounts from circulation. Demand side economics provides a more equitable distribution of wealth, and provides disposable income for each individual household. When one household spends money there is little effect on the general economy. When many people spend money an economy grows. That's why many businesses are "tourist oriented", because the more people spending money, the more money gets injected into an economy. Ignorance, and or,greed  are the motivators of trickle down , or voodoo economics. Tickle Down has created the scenario we have now, and it becomes more unstable, and unsustainable with each passing day. Bush/Cheney stole millions, gifted it to Haliburton,and left Obama massive debt on lies.