In 1930, Pluto was declared the ninth planet. In 2007, it was demoted to "dwarf planet" status by astronomers after considering new evidence. There are now only eight planets.
Also in the 1930s, the ideas of John Maynard Keynes came of age. In spite of a massive amount of evidence that these ideas don't work, unlike astronomers, economists won't demote Keynes's theories to the dustbin of history.
This isn't that surprising. Whether Pluto is a planet, or not, doesn't impact politicians, or their constituents. If it did, Pluto might still be categorized as a planet.
Keynes thought a free market economy should be managed: in fact, needed to be managed. His ideas flourished in the 1930s when the US was in the Great Depression. Keynes believed that a lack of consumer demand was the culprit to economic problems and government should spend to boost jobs and economic activity.
To this day, in the name of Keynes, economists and politicians support stimulus spending, unemployment benefits, minimum wages, and the redistribution of income.
Not only do politicians and bureaucrats get to increase the size of their budgets and take credit for benefiting constituents, but they get to do it in the name of helping the overall economy. They do it in the name of Keynesian economic theory.
But there is no evidence it has worked. Keynes's theories, as mentioned earlier, have been around for over 80 years. Countries all over the world have tried them. Government budgets have increased dramatically.