July 1981 is as good as a date as any. When good old Ronald Reagan introduced the concept of Trickle-down economics. 

Incase anyone here is unaware of how Trickle-down economics works, and it’s affects on society, I’ll provide a funny, albeit flawed, and not entirely correct, but not that far off of analogy... Here we go.  

Take a medieval fantasy setting. The king has declared that they well no longer bother the nice dragon living in the local mountains. In decades pass, a pervious king had send his armies to fight the dragon, and force it to obey the laws of the land. They dragon was taxed a potion of his horde every year to the kingdom. The dragon did not like this. Through this money from the dragon, the kingdom was able to build cities, roads, wells, fund innovation, and improve the quality of life for the people. But the dragon cared not for people, and wanted it’s “gold back.” As the decades went on, there were many kings until the current one was was appointed... One that was given much personal gold by the dragon to help him become king. This king said they would now only take a small amount of gold from the dragon, as with more money, the dragon could use that money to give people more jobs, and that would create more jobs and money, and improve work conditions, and people would actually make more money... Somehow... The king passed the new law, and the dragons wealth grew, and soon it’s horde was bigger than than any others. The dragon did not spend any extra money... Being a dragon. It slept on its pile of gold, and spent none of it, except to put a few coins here and there into the pocket of the king, and his advisors so the kingdom would not send armies against it, or dare touch it gold with their dirty human fingers. 

After many generations the kingdom begun to fall into ruin. roads were swept  away by monsoons, and walls crumbled with the turning of the seasons. So many problems of the kingdom could be fixed if it had more money, but the majority of the wealth of the kingdom was in the hands of the dragon, and he did not share. When the people of the kingdom grew vocal and angry, the kingdom hired more guards and soldiers, but not to protect the kingdom, but to instead make sure the king and his advisors would be safe. As the kingdom grew, it became a land of many peoples, and many religions. These strangers would be ostracize, and then criticized and looked upon with suspicion for forming small social groups apart from the kingdom... You know...Because of the ostracization. Over the years, as the people of the kingdom would face more and more hardships because of the dragon, the kings and their advisors would turn the blame to these “strangers”. The kingdom would be turned against itself, never achieving anything but causing the people pain. The dragon looked on, not with hate, curiosity, or joy, but with indifference as it did not care from man... Only gold. 

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So, when did people being able to “afford to live” become an extreme leftist view? Whenever the people started to believe cutting taxes on business and the rich would lead to... 

Instead of... 

Dragon take, and give nothing back. That why their pile of gold is called a hoard.

But dragons aren't real, and I’m not a economic historian so what do I know?