How has life improved under Supply-Side (Reaganomics) Economics?

I don't understand how people who aren't in the top 5% or so (or who have a serious chance of making it there) support Republican economics. It is indisputable that quality of life in the US has declined over the last thirty years, and for what? It is absolutely mind boggling that the culture war could have wrought so much damage. Economics is the only subject that should be important when people go to vote.