> When half the country has believed something for close to a half a century, across multiple generations, you bet your ass it needs to be debunked.

It dates back to the late 1890s (and has been criticized since then):

> In 1896, United States Democratic presidential candidate William Jennings Bryan claimed in his Cross of Gold speech that his opposition based their policies on the idea that the success of the rich would "leak through" to the lower classes, stating: "There are those who believe that, if you will only legislate to make the well-to-do prosperous, their prosperity will leak through on those below."[8][9][10]

> In 1932, humorist and social commentator Will Rogers wrote a column criticizing Herbert Hoover's policies and approach to The Great Depression and stated: "The money was all appropriated for the top in the hopes that it would trickle down to the needy. Mr. Hoover was an engineer. He knew that water trickles down. Put it uphill and let it go and it will reach the driest little spot."[11] In 2007, political commentator William J. Bennett credited Rogers for coining the term "trickle down" and observed its persistent use throughout the decades since.[12]

* https://en.wikipedia.org/wiki/Trickle-down_economics

so I'm not hopeful it will ever go away.

I had no idea the idea was so old!