system
Given the following post, respond as if you're commenting on Reddit:
human
[Economics] What are the differences between Keynesianism, Neo-Keynesianism, and Post-Keynesianism?
gpt
"Keynesianism" at large is just a moniker for a general line of research that takes on just about any number of definitions people want at the time. Neo-Keynesianism typically defines the post-war era economics present in schools like MIT and Harvard. The IS-L-M model by Hicks, and others who tried to mathematically formalize a lot of Keynes' writing from *The General Theory...*. Today, this has become 'New Keynesians' which describes the mix between fresh water schools of 70's and 80's with this line of research, effectively stating that in the short run there are economic frictions, but in the long run markets are efficient.

Post-Keynesians are (generally) a heterodox school of thought that believes that the entire line of modern research has entirely missed what Keynes was saying. They generally even reject a lot of the underlying microeconomic theory for it's assumptions of equilibrium.