“Trickle down” economics is an intentionally misleading metaphor. Water trickles down (but not up) because of gravity.
Money, on the other hand, circulates. When working class people buy gas at the pump, it benefits the likes of ExxonMobil. When they buy groceries, it benefits the likes of Cargill and ADM. A rising tide on the _demand_ side also raises all boats. Same logic.
Trickle down economics makes no more sense than trickle up economics. Each one prioritizes one demographic over the other. I think a more holistic view is what is needed.
It has to do with the relative spending velocity of the economic quintiles. The top quintile spends their money much slower and often just move it between their cohort. lower 3 quintiles spend their money quickly, and historically locally. Reagan started the shift away from taxing the most wealthy and the lower and middle classes have stagnated. Yes technology has pushed things worse with income distribution but the tax policies of the GOP administrations have worsened it greatly.
