It was effective when Ronald Reagan used it — remember? At the time, he oversaw a budget deficit that was then the largest in the nation’s history (blame it on Congress if you will, but a deficit-fueled stimulus is a deficit-fueled stimulus).
It seemed to be just the solution when George W. Bush smashed Reagan’s records for the largest deficits in the nation’s history (Of course, a chunk of the deficits were not “budget deficits” because reps kept both wars off the budget).
Perhaps a more accurate conclusion is that “trickle down’ has never been tried.
Every time we’ve been told it was being used, those telling us so were actually loading up a pig trough full of Keyensian spending increases.