And we've known it for nearly a century. Before it was called "trickle-down economics" it was called the "horse and sparrow theory"; if you feed the horses more oats, more will spill out for the sparrows to eat.
Problem is, everyone already knew "horse and sparrow theory" was complete bullshit, so they needed a new name, and "trickle-down economics" was the one they chose.
People are falling for the same trick by a different name.